That stays as part of the recording name - (Some Dumb remix) is a different mix and generally stays as part of the recording name as ETI that was always there. It is solidly part of the Recording name.
The (single version) dropping to disambig is mainly due to a Single that has been released with a Track called “My Cool Track”. And an album also having a (variation of a) track called “My Cool Track”. So we need disambig to tell these apart. They both share the same name, but sound different.
Whereas “My Cool Track (Some Dumb remix)” has always been called that name in full in the track list…
It is back to “What was this first called?”
I should also add it is really common to see (7" single version), (12" single version) and (album version) staying as ETI on many recordings and not being demoted to disambig. Sometimes it can just vary as to how many releases there are using that Work name. Different people follow variations of the guidelines - they are guides, not laws.