Description
[temp.type] does seem to suggest any two pack-index-specifiers whose expression is dependent are equivalent if their expression are equivalent.
If the constant-expression of a pack-index-specifier is value-dependent, two such pack-index-specifiers refer to the same type only if their constant-expressions are equivalent ([temp.over.link]). Otherwise, two such pack-index-specifiers refer to the same type only if their indexes have the same value.
quid of U...[expr] and T...[expr] ?
Suggestion
If the constant-expression of a pack-index-specifier is value-dependent, two such pack-index-specifiers whose typedef-name are equivalent refer to the same type only if their constant-expressions are equivalent ([temp.over.link]). Otherwise, two such pack-index-specifiers refer to the same type only if their indexes have the same value.