Nothing is absolute, of course if you take it far enough the seams of the argument tear but there is merit to it.

A senior browser frontend developer is likely to pick up mobile development quite quickly.

Likewise someone who's been doing Spring Boot Java backends for years and is proficient with databases, caching, etc. Isn't necessarily going to find it hard to switch to a serverless nodejs paradigm.

The network card person is probably able to handle the embedded microwave oven.

Etc.