I ve just realized, that the Tube SOP dont fuse the points when adding the end caps. Is it a reason why?

I think that we did this so that the side of the tube didn't blend into the caps which is what happens once it is fused. Either we give a tube that is fused and some people use a facet sop to cusp the edges or we don't fuse it and some people have to connect the points later.

An option for fusing the points would be one option.

Now that mantra has support for rendering based on vertex normals now, it would be nice if, across the board, houdini moved toward this paradigm.

This way the geometry would be connected, the point order wouldn't change because of the separation of the cusping, but you still get a hard edge and correct shading.