I can provide some first hand experience with this in conjunction with my G3X setup. I too have the VPX wired to the MFD - no reason why you can’t wire it to the PFD… but the fact remains, when your screen goes down, you lose control. I had an issue with my MFD where it’s kept rebooting in flight. I lost access to the VPX page.
In addition… I had Garmin help me troubleshoot some CANBUS issues. In order to do additional troubleshooting, I need to be in config mode on my PFD. When youre in config mode on the PFD, the MFD is also in “config” mode. When in config mode, you dont have access to the VPX… which sucks, because i need to remove devices one at a time until my network errors go down… that’s impossible to do through the electronic circuit breakers because I cant access them.
Just a few things to keep in mind. I dont regret my decision, however there are times when having the VPX wired like this is NOT ideal.