I personally think it's more likely the other way around, because tech like this isn't just invented overnight. Merc said themselves that they kept the FIA informed of what they were up to, so it's been known about for some time. It was probably too late to change the rules for 2020 though so they're doing it for 2021 instead.
Personally, if this system actually gives any real advantage then I think we would have seen it on cars before now. F1 teams aren't stupid, they're always looking for ways around the regs. This one seems too obvious to have not been noticed already if it had actual potential. I wouldn't be surprised if others have looked into it before but have decided that the cost, complexity, reliability and potential ban wasn't worth the investment. Not an issue for Merc with all their cash.