757/767 VNAV descent path angle during deceleration

[firstmrj]

Hi,

I looked into how the FMS of B767 construct the descent profile when simultaneous descent and deceleration was intended by creating some manually entered along-track waypoints at intervals of 1 NM.
In one case it shallowed the descent path to about 1 degree and slow the airspeed at the rate of more than 10 KT per 1 NM.
In other case the descent path angle remained at about 3 degrees and the deceleration rate was about the half of the former case.

In both cases, from my experience it seems we need speed-brake to achieve these trajectories in normal circumstances.

Any idea or thought about these difference?

Thanks in advance,