I'd take what you read on subreddits like this with a pinch of salt. A lot of people like to embellish or flat-out lie to either fit in, sound cool or to provoke a reaction (see "am I the asshole").
:shrug: there's definitely role-playing in there, but anecdotally, I know 2 close friends who did this during Covid and had 2-3 full-time jobs in non-software roles.
So I imagine the percentage of role-playing in r/overemployeed is less than 50%.
That's a non-trivial number of people, and I'd bet if you work for a large company, there's a non-trivial of people doing this now. (See the thread about Experion firing contractors with multiple jobs[1])