We could fix the upper bound being problematic to set in the first place right? If we say that an upper bound not matching isn’t allowed to backsolve by assuming maximum version support done by a comparison (< or <=) rather than exclusion (!=) should be interpreted as not supporting that version yet, and requiring this be monotonically increasing with time when present?
Put it into the specification that the purpose of an upper bound is only to say that a version is not and has not been supported, so backsolving to a version that did not have an upper bound at all is going backward in time, to even earlier in time, and further from any version that might know enough to support the python version.