That’s the impression I get too - that Quick Start achieves the same final result as using USB transfer via a computer.
(Although - I’m assuming that the “Encrypt iPhone backup” setting is on for the computer transfer, otherwise some data is omitted. I might be out of date here, though: I’m still using High Sierra and don’t know if that setting has gone away in more recent versions.)
When my wife upgraded to a new iPhone recently, we already had an iCloud backup, but we also did a backup to a Mac via USB, then used Quick Start. Using multiple systems this way takes a bit more time, but provides more options if something goes wrong.