I think they just decided to go with the distributions that have a commercial backing behind them (or, at least, their "free" versions). But I agree that Debian should be on that list.
Most of the Ubuntu knowledge is likely transferable to Debian. Dame with CentOS and RHEL. I believe yast is a bit different than both RPM/DEB? I could be wrong.
Anyways, if those are the choices, they make sense to me
Anyways, if those are the choices, they make sense to me