Too many assumptions in that question. I would note that I too have used synthetics of one type or another for almost 30 years, and never noticed consumption to be a problem.
That said, if you happen to have an exceedingly worn engine, that's guzzling whatever its fed, AND you switch from a dino with a low Noack test result, to a syn with a higher Noack percentage, then perhaps you might see your engine use more synthetic. Possibly, just going from a higher viscosity dino to a lower vis syn might cause the same effect.
But generally, all things being equal, engines do NOT use more syn than dino.
There's no reason for sustained higher consumption with a synthetic. Some synthetics will cause transitional consumption ..but that can occur between two synthetics. I'm of the belief that it's coke formations in the rings. One disrupts the other before forming its own ..or not.
I believe (but can't say accross the board or prove), that more oil consumption is more likely with synthetic but this is just my opinion derived from personal experience & accounts of other people who have said this happend to them.
I'm wondering if anyone can shed some light on the subject. My question is why do cars and trucks tend to use more synthetic oil between changes?
If an engine is dirty, and you introduce synthetic oil, the oil and it's additives will be "be used" cleaning the engine. As the oil loads up with the removed grunge there is a tendency for higher level of consumption until the engine is relatively cleaner. My belief is that this consumption is mostly at the piston ring interface.