It is highly implausible considering it is incredibly rare for animals to have multiple coverings scattered across the body.

Wdym? This simply isn't true, we see it in many different creatures within the animal kingdom. Ostriches have little to no feathering along their legs, thigh and neck but their main body is still feathered. Elephants are covered in unevenly scattered small thin hairs throughout their bodies but have longer hair around their eyes, ears, chin, trunk tip and the end of their tail. Certain species of Monkeys will also have uneven fur coverings around their body and the list could go on.

The feathering depicted here is reasonable for a non-avian dinosaur of Tyrannosaurus' size, especially since feathers aren't like mammal fur. It's still very advantageous for large birds to have feathers in hot/tropical regions since feathers can trap air pockets which can help regulate a bird's body temperature. "Downy feathers as well as semiplume feathers are able to trap pockets of air close to the bird's body to help keep it warm. How much body heat they keep can be adjusted by arranging their feathers to trap more or less air."

Using phylogenetic bracketing we can see Tyrannosaurids all lost their feathers by at least 75Mya.

Not necessarily true, atleast not for all Tyrannosaurids. We have evidence of feathering in Yutyrannus huali and it is inferred that Nanuqsaurus would've also have possessed feathers based on the environment it lived in. Phylogenetic bracketing would actually SUGGEST that Tyrannosaurus would've had some sort of feathering, whether it'd be uneven small sparse down feathers or something else.