That shouldn't be a problem unless the thickness of the tiles and plywood is too thick for the butterfly fixing.
You should be able to put the fixing in the hole, flush with the tiles and then use a long screw to fix the bracket.
There are a lot of different types of plugs anyway and if the one you have used works, and is sound, then that's all that matters in the end.
Gravity toggle bolts are another solution.
They require a smaller hole then the spring toggle.
Both are use once though as the toggle fall off if the fixing is removed.