> I think they adding a lot new stuff...

Yeah but there is also a lot of old stuff as well, just regular stuff like lines, etc...

There are various extension mechanisms in 3DM files so that it is possible to add in new stuff that can just be skipped by older readers, while leaving regular old stuff still in place and accessible. But they did not decide to do it that way for v5, unlike the Rhino v3 to v4 transition.

- Michael