A specialist discussing a complex topic uses that as shorthand based on shared context. Nothing would ever get done if every conversation required starting from "first principles" whether inside or outside academia.

What's missing in your claim is evidence that people in academia often mischaracterize this style of discussion from accumulated knowledge and shared context as "thinking from first principles". I don't see any plausible rationale for why they would.

Otherwise, using their typical mode of interaction from outside observations to infer they misunderstand first principles is not a standard anyone doing specialized work inside or outside academia would ever be able to meet.

The private sector would grind to a halt if discussing a specific IEEE 802.11 protocol implementation with a fellow SME required a lengthy preamble of networking first principles before answering in order to be epistemologically sound.

Similarly, using a conversation overheard at a conference to infer the experts lack first principles thinking would not be reasonable just because they appealed to IEEE documents instead of rearticulating the underlying decisions made by the standards committee.

Knowing what first principles reasoning is isn't the same thing as being willing to re-teach a discipline from the ground up for a stranger rather than first pointing to the existing literature that, perfectly or imperfectly, already addresses a topic.