Hi Max,
Sadly not. R19 has more care about it, but also there, it might be not as prestine (depends on how picky one is, make your tests!) as the original was, mostly around texture borders, etc. R19 is much better in terms of UV-island protection. Anyway, R18 and R19 are night and day in comparison, to be clear: R19 has much better results.
https://help.maxon.net/us/#OPOLYREDUXGEN
Sorry, but it comes with the process in R18, some polygon groups that might be spread over the UV map are sometimes combined in a single new UV polygon, which can’t be partially divided over the image to get the old relation back.
All the best
edited for clarification