[Accepted at the November, 2020 meeting as part of paper P1787R6 and moved to DR at the February, 2021 meeting.]

According to 13.8.2 [temp.local]paragraph 1,

Like normal (non-template) classes, class templates have an injected-class-name (Clause 11 [class]). The injected-class-name can be used as a template-name or a type-name. When it is used with a template-argument-list, as a template-argument for a template template-parameter, or as the final identifier in the elaborated-type-specifier of a friend class template declaration, it refers to the class template itself. Otherwise, it is equivalent to the template-name followed by the template-parameters of the class template enclosed in <>.

The intent is that a < following such an injected-class-name is to be interpreted as the start of a template-argument-list (and an error if the following tokens do not constitute a valid template-argument-list), but that is not said explicitly.