The CPU Tier List isn’t maintained by Amiibo Doctor, it’s actually its own separate research! The SmashCPU scene covers every Smash game and many, many other games as well. You can join their Discord server here!
You’ll notice that the CPU tier list and the amiibo tier list have some similar placements… I went into more detail on why that is in Could the CPU Tier List give us an idea of the I variable?
The above tier list is the January 2021 CPU tier list for Smash Ultimate. This is the early 2020 incarnation: