Well, I think context matters here a lot:

If you go to a random lawyer in Wyoming and ask them to write "expert opinion" then what you'll get would probably be something standard, written by a junior associate, or maybe even produced by ChatGPT.

If the White House orders "expert opinion" on potential Supreme Court ruling then the chances are that the expert asked to prepare it is someone who plays golf with some of the SCOTUS judges.

So those two "expert opinions" might not bear the same weight.