WebRTC is in fact no issue at all for a number of reasons.
First of all, it doesn’t work, when using the TBB, as the TBB is compiled without the necessary additions for WebRTC to begin with: https://lists.torproject.org/pipermail/tor-talk/2015-February/036845.html That’s why, as long as you use the TBB, the issues which arrise, thanks to WebRTC are non existent.
Even if you would go so far as to use a different browser, which is absolutley not recommended, it wouldn’t be much of an issue, as Whonix per design, like you’ve mentioned, only shows the IP as 10.152.152.xx. This would, if you used a not recommended browser, like you’ve said, hint upon the fact that you use Whonix, though Whonix actually doesn’t activley hide that it’s used and is per default not really designed with this in mind.
So, in conclusion, stick to the TBB and you will be fine.
Have a nice day,