i totally see how it could be one thing (regarding going off the derech because of slits) remember how chamets and matzah are so linguistically related but when you look at the ches and the hay-
what is the difference?
a litle line, thats all it takes, to go from matzah to chametz. this makes sense to me. and thats why we have so many fences, and chumros to stay so far away from cases like the slits to going OTD
While tznius is probably the most multi faceted topic, one main reason is to be a fence, or a “siyug latorah”(pirkei avos)