[intro.defs] Why is `\termref` rendered in italics?

In [intro.defs], we use a different style of referencing subclauses than elsewhere in the document. This is rendered in italics, which suggests that there is a definition:

draft/source/macros.tex

Line 388 in 458b16a

\newcommand{\termref}[3]{\textit{#2}{#3}\iref{#1}} % in Clause 3

For example, the occurrence of diagnostic message in [defns.undefined] is rendered like this:

Is there some reason for this unusual style? Should we just drop the \textit?

I've looked through https://www.iso.org/sites/directives/current/part2/index.xhtml and the Introduction in N5001, and there doesn't seem to be a reason for this typographic choice.

Isn't it consistent with the style in https://www.iso.org/sites/directives/current/part2/index.xhtml#_idTextAnchor007 ?

References to other terms defined in the Terms and Definitions clause are in italics.

Yes, ISO/CS has asked us to put those cross-references in italics. See

https://www.iso.org/ISO-house-style.html#iso-hs-s-text-r-r-ref_clause3

To cross-reference another term listed in Clause 3 as part of a terminological entry, put the referenced term in italics with its reference number given in brackets afterwards.

Git blame shows the style macro and the cross-references within the clause were introduced by eb7f0bc to respond to a comment from ISO central secretariat. The comment explicit said to format them in exactly this style.