The consensus seems to be that the software updates GM applies when the pack is replaced results in maybe a little more conservative charging profile.
My experience with a 2018 is that while the slowdown on DCFC started at ~55% on the old pack, it starts close to 50% now. But the old charging profile on the older Bolts like mine took big step-downs and now it only drops in 1kW increments so more of a curve. Overall, DCFC times are probably not significantly different.
How that relates to the newer models, I couldn't say from experience but the charging profile should be the same on all model years now since we all have the same pack chemistry and capacity now.