RZ
We've been allowed to managed non-precision approaches for the last 9 years or so,even when the a/c didn't have GPS.
In fact I've seen more duff managed approaches using GPS in a non WGS84 environment (China) than ever before when all we did is check that we were in 'high' accuracy!
The validation of the approach came about because there were some approaches that had a level segment (FPA =0 deg). sometimes this would be shown in the FMGS as 0deg and sometimes there is no glide angle but the system tries to fly level. In the latter case the FPA is not 3 deg or whatever. In our database this means a few approaches are banned fom being flown.