The Language Steering Group discussed today what should be done here. At the time this proposal was accepted and implemented the deprecation part of the implementation was postponed, but then never revisited once Swift 6 drew near.
In discussing the behavior previously accepted (that #fileID be deprecated in Swift 6), the LSG determined that there was no longer consensus that this remains the correct path forward. As such, the LSG has decided that the proposal text should be updated to match the current reality (or at least edited to note that the deprecation portion of the proposal was never realized). The status quo will be that #fileID remains supported.
There was some interest in the direction mentioned by @grynspan above (eventually deprecate #file and require users to choose explicitly between #fileID and #filePath), and the LSG invites further discussion about whether such a change would be worthwhile.