I don’t think your assumption on how well I understand how the professional world works is correct.

I understand very well that signing any NDA is by no means “zero risk”, it has a definite risk attached to it. Declining it is costly in some way, but also has definite advantages.

I also understand that very rarely is the phrasing ever “this conversation will be off the record”, but rather some phrasing including the specific topics that may not be shared, like you say for example, product details. Blanket phrasings like this are always very sketchy.

This is not a proper talk by meta that you could just “hear them out”. They explicitly said off the record and confidential, there’s no reason for that if it’s something innocuous. There 100% would be an NDA involved.

The fediverse is all about being open, starting with an NDA is definitely not “zero risk”, you can not slip up ever, or you’re going to be destroyed by lawyers, this is the exact opposite of “zero risk”.