The current tag wiki excerpt of topolect is:
Questions regarding regional variants of the Chinese language.
which is spot-on. The definition of the word "topolect", specifically applied to Chinese, is:
A regional variety of Chinese; especially a lect other than Standard Mandarin.
Assuming that the terms "variants", "variety" and "variation" are equivalent w.r.t. this discussion, from these definitions follows that [regional-variation], for which no tag wiki excerpt is given, is effectively included in [topolect].
A tag synonym seems warranted. However I believe this requires a mod intervention, because of all users who could vote on this synonym (7), only one visited meta in 2020 (Mo.♦), and half of them haven't been seen for years.