It is a feature, which I don’t want to remove 
I just mean that if the brush tip is already included automatically, it shouldn’t try to be included twice and shouldn’t bother the user. I’m pretty sure this error message is just a bit too eager, telling an error in case of quite a normal situation (considering that in previous versions of Krita you did have to add the brush tips yourself).
Also btw, right now the presets include the brush tips inside themselves (which I hope will be optional at some point) so there is even less reason to try to fit the same brush tip to the bundle multiple times. Krita should notice it’s the same resource, not just the same filename, add it only once and proceed like normal.