I think the FMGS can only provide predictions when you have an AP/FD mode engaged. With automatics off (and therefore selected speed also) there is no requirement for any guidance... so you don't get any.
e.g from FCOM 4 ..... Note: The ND does not display the TOD hockey stick when HDG (or TRACK) mode is engaged.
So with no modes at all you will get even less!
Phase switching to DES requires "initiating descent" (FMGS Operational principles chapter) ..... when you fly raw data you just alter the pitch attitude, you do not "initiate descent" in FMGS-speak.