I don't think so. The phone charges at a faster rate until 70% or 80% and then charges at reduced speed till 100%. This mechanism was also present in Nougat. In Oreo it takes almost same time as Nougat for complete charging (about 2 hours). The only new thing here is the 'charging rapidly' notification text on the lock screen.
no i don't feel any rapid charging, and also i don't see any charging rapidly notification on lock screen
in Nokia 6 with Oreo Beta i noticed today that when Aida64 app reported charging rate 1.7A or 2A lockscreen said "charging rapidly" so mayby it's change in reporting when charging power is over 1.5A .