The stacking effectiveness in Granblue is complex and largely arbitrary. There are many "Special Cases" in stacking which cannot simply be explained by logic. And then there are so many areas where stacking discrepancies can happen, e.g. Elemental ATK buffs, debuffs, Bonus DMG buffs, etc.
Back to the main point, single-sided and double-sided debuff distinguishment is iirc simply one of the many heuristics players deducted to see if things stack. It works to a certain degree but there are definitely cases where this heuristic doesn't work (most notably Drang and Ferry(Grand)). Obviously we would like an exhaustive list of stacking relationships, and/or better heuristics to judge them, but it's also very time consuming to test and exhaustively list. In my opinion, there's no simple way of making these things absolutely clear.
But to answer your question: is there a clear distinction between single-sided and double-sided debuffs? The answer is yes, single-sided means one of ATK/DEF like Defense Breach, and double-sided means both ATK and DEF like Miserable Mist. However, like the wiki page mentions, MANY exceptions exist. I prefer the name "Mist category" and "Non-mist category", but I guess it's just as unclear as what we're using now.