[numeri]

It makes quite a lot of sense juxtaposed with "train time compute". The point being made is that a set budget can be split between paying for more training or more inference _at test time_ or rather _at the time of testing_ the model. The word "time" in "inference time" plays a slightly different role grammatically (noun, not part of an adverbial phrase), but comes out to mean the same thing.

[quantadev]

Exactly right. The term "Test Time" had relevance in a certain context, and in a certain paper, but once people read the paper and saw the term they latched onto it, not realizing how totally non-descriptive and nonsensical it was when used outside that specific narrow context of genuinely "testing".