If we start routinely back-patching things that fall into that category, we will certainly manage to destabilize older releases on a regular basis.
Just because something is bad if done in excess doesn't mean specific moderate partaking is bad too.
We actually did backpatch the NaN stuff and reverted that because, for me, it was a silent change of functioning behavior. I find the decision to back-patch this syntax oversight considerably more obvious than that one was.
