Seems the same across Boeing fleet
Be careful of that kind of quote. I used to fly the B757 and B767 and as has been pointed out above, there is no speed protection when using VS mode and it is possible to fly away from the selected ALT. Normally used for non precison approaches where the go around altitude is selected and the a/c is descended using VS to the MDA.
On the B737 which I fly at the moment, there is full speed protection in VS mode but you can still fly away from the selected ALT, again used for non precision approaches.
As far as I remember, on the B757/767, you had to preselect another ALT before you could use VS if you were already in ALT HLD mode. On the B737, selecting VS whilst in ALT ACQ only arms VS as denoted by a white V/S annunciation. A different ALT has to be selected (more than 1000ft difference) before you can actually engage VS.
I stand to be corrected though.