I think this is much more reasonable when you aren't on a tight timeline to open the Rift. Like I understand why you would make this your SOP when you're researching seals alone in the woods and I actually agree with it. If there is no time pressure you can take as much time as you want.
The fact that he seems impossible to convince that this is not the best strategy to use in this situation is why I think he isn't reasoning clearly. Recall when we had to hide that we weren't using full prep on the MS chain? He refuses to adapt his principles in changing situations, instead forever enshrined them as "this is the way it must be done".
He will begrudgingly accept that Hazou does this, but it calls his judgment about decisions like this into question.
I remember when we first had that talk, from the other side, with Jiradad.
If memory serves, his points were mostly "I can, because I have A-rank jutsu and the skills to deploy them to destroy just about anything bad, a whole village to double-check my work, ANBU ready to help, and a Boss Summon at the ready."
Still, our minor rift-type sealing failure (meeting OliWhail) had him on edge and checking for many things.
My point is we have only one of those, and we're going to try to make a stargate to wherever. Kagome's precautions are, I believe, reasonable due to his experience and our situation.
And tbh, I think he is thinking clearly but with different goals - he's very aware that he's optimising for safety, not for results. He wanted to go down in history not as the best sealmaster/teacher, but as the safest. Losing no students, always adapting for best safety, was always his goal.