"Knowing" (guessing really) what is possible and not is a huge deciding factor in if you can do that thing or not, meaning if you "know" it isn't possible you'll probably never be able to do it, but if you didn't know it wasn't possible, it is possible :)
My hypothesis - this may be the key, but in the other way. LLMs are known to mistake negative instructions as a positive ones. "Don't use Tech_A", then Tech_A is subsequently used because it was explicitly named in the query. Especially when the query is long, complex and there is a lot of context. "Forbidding" LLMs to do stuff is a common mistake, which goes hand in hard with anthropomorphizing them.