If it's any consolation pretty much all of the very highly rated games of the past two gens have these anomalies knocking them down a point or two.
One thing I've noticed is they often come a week or two after the reviews stop appearing, which really makes me think it may in part be about getting as much attention as possible. I recall with BotW it was at 98 for some time until, a couple weeks in, two 70's and a 60 suddenly appeared. Just seems suspicious that the most anomalous reviews often appear to target releases that would result in the least competition for attention.