I’ve never heard a grown man referred to as a “boy” except in the pejorative sense/as part of a turn of phrase.

Here's [1] an example of using the word "boys" to refer to young men on a college football team in a way that I don't think fits either category. I used a northwestern fan site given the email address in your profile, but I found similar examples across lots of different sites.

[1] https://www.insidenu.com/2017/8/30/16200774/northwestern-foo...

'Boys from the Blackstuff' :

https://en.wikipedia.org/wiki/Boys_from_the_Blackstuff

'American Red Cross – Our boys need SOX' :

https://propagandaposterstore.com/product/american-red-cross...

'Old boy' :

https://dictionary.cambridge.org/dictionary/english/old-boy

edit - could also just go straight to the entry for 'boy' :

'a male child or, more generally, a male of any age'

https://dictionary.cambridge.org/dictionary/english/boy

It's common in my friend group (late 20s, early 30s) in CA, and as far as I know, it's also common farther out than that. Not pejorative.