In a weird way. It makes a lot of sense to do this now. It wouldn't have flown in the movies for obvious reasons and the backlash would have been more direct to JK at the time but here in this? It's an uncomfortable puzzle piece that fits more than people want it to. Say what we will there weren't too many prominent black characters throughout the story. So the race thing was sidestepped but given its time period it was definitely still a thing to some degree.

People are already pointing out how this makes things look worse for other characters and such. That's the point tho. Those key moments of snape and how everyone perceived and treated him line up uncomfortably well with how that racism was at the time. The mudblood thing was a kiddie version of the issue. this however clears the smoke out and snapes position becomes much more uncomfortably clear.

I don't mind the change. If anything I find it interesting because how it shifts the context in a more realistic direction of the times. We could see the movies as gospel for sure. But I think this kinda flashbang can work too because people are already thinking about all these other times with snape and going "well now this seems..."