H1B and EAD?

I am currently on H1B status and recently received an EAD card thru AOS (marriage to USC). I know if I work using my EAD card, I am no longer in H1B status (in theory). But how does USCIS enforce this? I'll say that I do want to stay in H1B status until I get my green card just for my own peace of mind. But I am also considering helping a friend's company with a short-term project (8-week gig) and wondering if I could use my EAD for that? I am curious how would USCIS know I used my EAD for another short-term employment? Obviously my I-485 application has already been submitted to USCIS, so I have no reason to voluntarily declare or report my employment plans to USCIS at this point in time. And so practically speaking, how will I automatically lose my H1B status? Does USCIS ever check IRS records?