On both Airbus and Boeing, the yoyo/V/DEV indicator profile is always lower than that of the VSD. This results in confusion and the VSD being made slightly redundant.
Another behaviour that I have noticed is that prior to the nose pitching up to lose airspeed, eg 250/10000, the plane goes a few thousand feet below the profile, or rather the profile suddenly jumps up a few thousand feet, so I guess the plane can re-intercept it. However, in real life, these level-offs are accommodated by the VNAV profile itself, so the plane can slow down while staying exactly on profile.
I am also curious about how you have programmed the VNAV to calculate its path. In real life on Airbus and most Boeings, the plane will descend in idle thrust to the first restriction, and thereafter maintain a so-called ‘geometric path descent,’ meaning that it will aim for a continuous descent between any two constraints, without levelling off. This may not necessarily result in engines being at idle thrust if the path is shallow.
In aerofly, I’ve noticed that the plane typically levels off at a constraint, and wait until the point where it can reach the next constraint in an idle descent, but this often results in an unreasonably high V/S.