RWU,
I wouldn't recommend coming back to green dot no, however the method is still safer than using a v/s mode which overrides speed which could result in a stall. IMO. I've not had an issue with selecting Mach in open climb and coming back one or two decimals. I have however seen speed decay when others are concentrating so hard on climbing to an altitude using V/S and I won't ever use it at high altitudes to climb.