Sure - it just irritated me as that was what I was doing, and then at another time pants was also not accepted - there is no default. Just as there is no default for sinä/te etc. I am aware that the volunteers work really hard on this but cannot help the irritation sometimes.
"To fit" is either "istua" or "sopia", the related nouns are "istuvuus" and "sopivuus". I'm just guessing, but I suppose that "istua" ("to sit") comes from the fact that the clothes you wear sort of sit on you, well or poorly.