You should worry not, that's of the built in filters default settings.
It doesn't change the visual appearance.
There are cases though where there are some artifacts within that filtered area outside the original object though, but not with the built-in ones.
Blurring, glow effects and dropshadow exceed the original object areas and usually it's the other way around -it is necessary to expand the filtered area so the effect won't be cut short.
All in all if you don't like the visual bounding box expanding, switch to geometric bounding box in the preferences.
(Which shouldn't expand if you add a thicker stroke either.)
