Proubuilderizing model makes VertCount go up by 300%

If i probuilderize an object the vertcount goes up by about 300%!!
(even though you put the whole model in the same smoothinggroup) This is probably because every triangle in the Uv is a separete shell?, highly unoptimized (and a also pain to work with). Or is it something else that causes this, like it auto generating uv2 uv3 uv4?

Is there any way to reduce the number of Vertices in the model so that it has the same amount as the unprobuilderized object? I have tried Collapsing uv or weilding uvs but it makes no difference.

Thanks!