Well, nothing immediately explodes as soon as you do, but generally:
That's a usability feature. Just by having the non-free repository enabled by default, nonfree software does not automagically install itself.
whonixcheck will report any nonfree software. Except for some hardly avoidable packages which are in the
I don't know if it's a good idea to disable the nonfree repository by default. It would be more Libre Software advocacy hardcore than Debian itself (which has these enabled by default). Users failing to install their nonfree package then would submit support requests. On the other hand, advocacy of avoidance of installation of nonfree packages may be better. I guess we have a quite balanced approach to this with whonixcheck currently.