Multi-part grouping not applied & misleading performance counts

(Since hyperion offers nice bulk discounts here’s another problem with a hyperion release.)

For this album

Roon presents me the following (non) grouping of the two multi-part works with consecutive parts the album contains:

Why aren’t the Walzermasken and Triakontameron not grouped as they should be?

I mean, even allmusic knows about the grouping:

The resulting performance counts are wrong in my opinion, too.

Is it a deliberate decision to not group “incomplete” multi-part works or is it just not done for this album?

BTW, when I switch to multi-part grouping according to file I run into this again:

At least I know that this - even so it seems wrong to me - will probably not change …