Hey MarjaE and thank you for the enhancement request. If you'd allow me, I'll give my oppinion related to the above suggestions.
Generally speaking, a bug verification has two purposes: first to make sure that it does what the fix describes doing and secondly to ensure that there are no regressions introduced by the fix. Obviouslly, for beeing able to follow through with a verification, the following are required: having the required knowledge, capacity and hardware to reproduce the bug on affected builds and then not reproduce the bug on fixed builds. As you are aware, in software developement it is expected that sometimes, there is a disjoint betwen what the specification requests - here the bug report - , what the implementation actually does - the fix - and what the testing people can or actually test - the verification - . Imagine this gap getting emphased by not having the exact particularities of the person who reported the issue and who was not part of the implementation/verification process.
Therefore, particularly in the accessibility area, there's a certain gap of specialized people who can or would do verifications, so it is often the case that a fix that is deemed as complete implemented and verified as such, only to have it spin up later in follow-ups as a specialized eye was thrown over.
Given the above context, everybody expects that a resolved fixed issue contains a patch or a series of patches that fix a problem or a part of the problem. Often is the case in which multiple issues are present in a bug report and follow-ups are spinned starting with the initial report but there are also cases in which the spin-ofs can happen at a later time after the initial fix. Hence a complete resolved bug might turn partial fixed at a later date, but having a status to reflect that would not affect any follow-up fixes or follow-up verifications, since those are going to be handled in the spin-offs anyways.
Overall, it is my oppinion that introducing intermediary statuses would only complicate things, since all the bugs might be part-fixed or part verified depending of the point of view or depending of the timeframe.
Hoping that the above wall of text makes sense, please feel free to add more context or clarification if I missunderstood anything.