Will wait for @Michal Kubecek's response about the manual page update
and as second possibility: options to update ethtool help string.

IMHO, yes the comment in ethtool.h enum definition is good
as it helps developers who use ethtool.h directly but from
ethtool app USER point-of-view, the manual page is the
first impression and ethtool --help is second. The effort here is
to help the user with a clarification, to avoid the clear confusion
with the wrong naming of 10000baseCR

Is there confusion? git blame suggests it has been there 10 years, and
this is the first time somebody has questioned it.

I would limit changes to Documentation, man pages, help etc.

	Andrew