I think the issue with internet Raid rarity is the competitive value of the Pokemon itself. It took me ages to first encounter, the successfully join a Raid for Skuntank or Stojourner (Scarlet exclusives, I'm playing Violet). But Armarouge was no problem, and I saw it all the time. I would see Blaze Tauros at a fairly consistent rate, but wasn't able to join the Raid for quite some time.
Pokemon that are seen as less valuable in competitive are much less likely to get hosted by players who encounter them, which will inherently skew the "rarity" of a particular Raid.