It might be "true to the setting" but it's also completely wince-inducing from a modern perspective. Like if any real world researcher thought like that, I'd hope they'd get drummed out of any institution they were a part of. In shame.
Its actually a very new attitude from a historical perspective. Free flow of information that is. One of WW2's stranger effects on America was that so very many people got taken out of the workforce and so many random women got tossed into it that it broke the equivalent of the Guild system. A lot like the Black Death broke the social order by sheer attrition, old power structures just imploded. When the people got back they started this thing called the 'Do It Yourself' movement. DIY meant knowledge of hoarded skills where suddenly up for grabs do those who could pay. People randomly gained skills in things that weren't their actual profession and the market for materials to do DIY stuff got to the point is was standardized instead of mass produced.
This may seem like a minor thing, but if you've ever dealt with houses from before that time period you know the truth, everything is of nonstandard size and angles are weird. Nothing is straight. Groups made their own custom parts on seemingly random scales so you had to hire the same people over and over again or risk redoing things till you ended up on a different random scale of parts. Finding windows that fit the old window frame is a convoluted, luck based missions that involves silly prices or reworking the thing.
Companies are still trying to get back to those 'good old days'. You can tell by the way they've invented dozens of different screw heads. Philip's[+] and flathead[-] used to be a matter of size and many screwdrivers could handle most of those types. Now we have dozens of incompatible square head sizes, equally random triangle head, and random prong number star bits for little reason beyond greed and the bits for the changable drivers are often soft enough to break after half a box and good luck finding replacement bits after a few months.
Lets non spend too much time going over how once they got those color mix codes on paint they started randomly switching around the names of paints at the same store every few months/years. Same name on different colors, because... pretty much just because the can confuse you int buying the wrong paint under the same name.
Holding the snakeblood as our personal shiny for research seems both suboptimal and greedy. We're damn good at this magic stuff, sure, but we're not Gold-Wizard good at research and it's not like shared credit actually hurts us much mechanically. This is especially true if it ends up being something that requires a lot of actions sunk into it to actually make something worthwhile from.
There is the simple matter that you don't reward bad behavior. He wants to play mind games with people. Letting him play with what may be a unique substance is a reward for his past behavior.
There is also the matter of it being a good idea to do the preliminary research yourself before bringing in outside help for a second opinion. Letting him in on the ground floor means admitting to him you need the help to do anything about this because you can't do it yourself. That is the reason Mathilde failed to just hand the 'box of snek' off to the college originally.
Gold is the color of logic. I believe he is acting logically. We already know one of his goals, the study of skaven tech, but what goal would have him hiding his true strength and distancing himself from his fellow wizards?
Nasty truth about logic is logic is not infallible, only internally consistent. Also it can be completely flawed and based on bad information. People hear the world 'logic' instant think its made of smart.
Logic is like statistics in that it says whatever the hell you want it to. You can give a hundred students the same statistics (exact same statistics) and get dozens of radically different, mutually exclusive results. All logically rational results.
Also, let us never forget that 'Insane troll logic' is in fact a recognized type of logic... if one not respected and commonly derided. He must have a reason or twelve for why he wasn't sharing said logic... which he doesn't apparently feel like sharing with MC. Even in private. There is little to no reason to let him into MC's confidence without him letting her into his. He didn't even make smug, self important attempt to weasel his way in.
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I am in agreement with you that without knowing his logic, its very hard to actually evaluate his logic.
Again, triple digits of cash would get Mathilde "one bookshelf" of books.
Sigh... this is why you charge admission to the public section of the library in books. They want different tiers of access they need to show up with 'donation books'. a little grey mage rumor control and people buy those books for you. Some plan to act all grey wizardy and get people to gather your shinies for you would be nice.