[Accepted at the November, 2020 meeting as paper P2096R2.]

It appears that partial specializations of variable templates are intended to be supported, as 13.4.4 [temp.arg.template] paragraph 2 says,

Any partial specializations (13.7.6 [temp.spec.partial]) associated with the primary class template or primary variable template are considered when a specialization based on the template template-parameter is instantiated.

However, there is no explicit specification for how they are to be handled, and the wording in 13.7.6 [temp.spec.partial] and its subsections explicitly applies only to partial specializations of class templates.