Indeed we use the speed trend, just reread my own post..... Both for EFATO and the Eng Fail in CRZ (obstacle) scenarios. Indeed it is not desirable to decelerate below green dot.
The descent may be shallow or not, in fact it depends on FG software. Some older aircraft use a different ratio for speed/altitude trade-off. Another reason to not pull OP DES until the trend vector touches GD.