Yeah, I'd have this issue as well-- patina develops as a result of normal environmental processes taking their effect on the bike. By 'preserving' it with some sort of chemical coating, it's trapping the appearance of the patina but it's still a modification of the finish. A 'patina purist' would let the patina continue to develop organically.

Honestly, while I can understand the whole patina obsession, I don't buy into it. I like my bikes to look nice. I like nice finishes. I'd repaint any classic bike, as long as the paintwork was done as well as if not better than the original. Or, let me put it this way-- I like to view the historical essence of some of my bikes through the perspective of seeing them as the original owner might have when the bike was brand new. Others like to see patina as a record of the bike's usage. To each his own... but for God's sake don't give me the whole 'patina is sacred' line, I don't buy it.