I’ve declared an emergency once, but it was on behalf of another aircraft. I was assisting a pilot who had lost his engine, he was busy aviating, and I made the decision to declare for him with ATC. He landed his aircraft safely and as far as I know there was no investigation or paperwork of any kind. I was given a number to call, but it turned out it was the ATC facility itself and they just thanked me for helping.
This goes with the advice I was always given, which was never hesitate to declare an emergency if something is going bad. I first encountered this at a seminar at which the speaker asked everyone in the room who had ever declared an emergency to raise their hand. About a dozen or so people did, at which point he said, "Keep your hand up if you had to submit paperwork afterward. " Every hand went down. Now these were general aviation pilots, not professionals, but I thought it was a good point.
But I think you’re asking about a pilot frivolously and intentionally declaring when there isn’t a good reason. I have no doubt a pilot doing so would face consequences, professional or not. I still don’t think there’s a reason to think that in this case. In my mind this is mainly about a conflict of interest between a crew and ATC, the crew solved it a bit heavy handedly maybe, but they were not necessarily wrong to do it.