That's variable where it does apply and it doesn't apply to all rifles. Most will experience a POI shift but it's repeatable and it just shifts the group position. Almost every rifle I've ever tried it on (that's somewhere north of 500 now) has behaved like that with Magenetospeed. The exceptions I could count on my fingers. I always get a zero without the MS and then shoot a group with it so I know the offset and that just ends up in the gun's data book. I use LabRadars too but IMHO the UI is a PITA, it drinks batteries and it's big and relatively heavy and I'm always losing the straw out of the sighting notch so the irritation of using it is pretty big. Then again, I also have a number of optical chronos from Chrony and ProChrono. I just don't use them much.
Like someone above said, there are benefits and costs to everything.