[tex4ht] should nameref.4ht be TL sources for tex4ht?

[Karl Berry]

    I am only reporting what I found.

Yep, I understand. It remains a mystery though :(.

    https://www.12000.org/tmp/texlive_cygwin/install-tl.log

All looks fine. tex4ht got installed. And nameref.4ht is part of
tex4ht. So strange.

    But if no one else reported this, 

Indeed, no one has.
Although the number of tex4ht users on cygwin might be = 1 (you).

Well, it will be interesting to see if the problem repeats with 2018 (or
whenever you install again) ... --thanks, karl.