Well, subj.
If config option is set to "Start in Atum" player will respawn in Atum indeed, but not at his bed.

Forge: 36.2.2

Due to how spawn points is handled nowadays, this is borderline impossible to achieve.
As it´s working for its current intentions, with starting in Atum and playing there, this is very low priority.
Might get around to it at some point eventually.

Should be fixed by #391 :)
Might be a little while before a new build is out though, as I´m not home.