Semantics aside, you and
YVR Cockroach are saying essentially the same thing.
But, lest the "hidden city" concept gets lost in the shuffle, I simply want to point out that FCO-LAX nonstop is monopoly product offering of ITA, whereas a dozen airlines sell BRI-LAX with a single connection. Therefore, ITA can command a premium for the former. Furthermore, when you attempt to change from the latter to the former, it's logical to get hit with the fare difference, regardless of whether or not they charge an additional fee for the change itself (some fares have change fees and *some OTAs assess their own service fees in lieu of or on top of these).
Most airlines operate this way, which is why in pretty much every airline forum on FT there are threads about taking positioning flights to random outposts to start trips and/or terminating trips at hub airports even though the actual destination is a random outpost.
Ditching final segments is usually pretty easy, but striking hidden cities on the front end or mid journey is not (unless you're prepared to pay up).
*OTAs adding their own fees is the only part of this process that could possibly rise to the level of "scam". But, when these fees are present, they are usually disclosed upfront, and there's a decent chance that you chose to book with the OTA because their upfront price was favorable.