Proposed resolution (approved by CWG 2025-09-12):

Change in 7.5.5.3 [expr.prim.id.qual] paragraph 2 as follows:

A nested-name-specifier is declarative if it is part of

• a class-head-name (11.1 [class.pre]),
• an enum-head-name (9.8.1 [dcl.enum]),
• a qualified-id that is the id-expression of a declarator-id (9.3.1 [dcl.decl.general]), or
• an elaborated-type-specifier of an explicit instantiation (13.9.3 [temp.explicit]), or
• a declarative nested-name-specifier.

Explicit instantiations with a nested-name-specifier do not seem to be declarative, but should be.