Are the “terrible twos” real?

My 23 month old is a happy, outgoing, fun guy most of the time. He’s definitely been developing more preferences and has strong opinions and gets understandably frustrated when struggling to express them. But just the last few days he is so demanding, impatient, and whiny. Is THIS the terrible twos?! He’s been eating ok, but appetite has been down for a couple of months now. Sleep is ok, has never been great but he’s getting about 13 hours total a day. His naps are frustratingly short and always have been. No changes in routine. The first day I noticed this, he asked to take a nap at 5pm and then vonited 3 times. He clearly didn’t feel good that night and the next day but has since seemed to return to normal . He has bursts of his usual self but I can’t figure out what is going on. Any tips appreciated!