There doesn't seem to be any pattern at all on the VHF high band.
When I first started scanning in the 1970's, I don't recall any repeaters in the VHF high band for public safety. Since the band was already occupied when VHF repeaters became popular, it would have been difficult to establish a standard offset without relocating other users. This would have been a time consuming process at the time, when you consider the radios of that era were crystal controlled and trunk mounted.
Additionally, the band was dotted with different radio services...business, utilities, taxi service etc, that would have made it impossible to establish a standard.
The 450-470 mhz band is pretty much a 5 Mhz split, with the lower frequency of the pair being the transmit side of the repeater.