I didn't think DC charging balanced the battery!If you have a Zoe the rate will drop off a cliff at 99%, but this is because it's balancing the battery cells. Not due to any charging regime. Can take up to half an hour though. Best done on your overnight charge and does need to be done on a fairly regular basis.
I don't recommend you balance cells on a rapid though. You'll make no friends that way.
In principle yes, the last (and first) part of the charge cycle of any lithium battery is always slow (watch your phone or laptop charge, they'll do the same). When this happens and whether you notice it or not depends on how they've designed the car. For example, my PHEV charges at 16A max from AC, but the last hour or so of the charge cycle is noticeably slower as it gets near the 100% reported SOC.Does the charge rate vary depending on the SoC?