Hmm, I see Laurelorn's play here.
By inviting the Druchii to the diplomatic table, it sends a message to Ulthuan - "do you want to get your own foot in?".
That the Druchii intel is untrusted does not matter, because it has created the following scenarios:
-Ulthuan offers no deal, We take the Druchii deal -> Ulthuan loses influence, Naggaroth gains influence, Waystone network in danger no matter what.
-Ulthuan offers no deal, We refuse the Druchii deal -> Waystone network in danger from blind experiments, they cannot make a deal to make us stop, because they'd have to deal with Laurelorn aligning with Druchii if they lean on the Empire to make Mathilde stop, and Naggaroth would be alert and ready to take advantage if they try to force the matter.
-Ulthuan offers a deal -> We get to next level negotiations where its now Ulthuan trying to make a deal to impose restrictions on what we get to play with while Naggaroth offers a suspect deal but one that we theoretically can take if Ulthuan's deal is too unfavorable.
Laurelorn and Mathilde's best position here is thus to be intererested but not eager for a deal. We want to make small transactions for verifiable lore, but we absolutely do not want to commit to Druchii joining the project in any shape or form.
Naggaroth's best position here meanwhile is to escalate the Marienburg situation while we talk, to weaken Ulthuan's bargaining position because they have to choose between their Marienburg interests and their Waystone interests, they benefit no matter what. Their first bits traded are unlikely to be straight up hazardous, these are elves and they play the long game, the most is that they'd give genuine information, but with the safeties left out as a test.
Ulthuan gets to choose between getting screwed on many things...or swallow their pride and recognize Laurelorn proper. Which still has them screwed in domestic politics, something the Druchii will exploit.