I think some of the flight duplications will continue during 2022 to to keep the Heathrow slots utilised. It is interesting that the flights transferred from Gatwick have kept their
Gatwick flight numbers, the 2xxx series. I think from Summer 2023 some of these flights will return to Gatwick. However some flights to popular destinations have previously operated form both Heathrow and
Gatwick and will continue to do so.
Malaga for example this summer 2022 is up to 4 or 5 daily from Heathrow, whereas previously it was rarely above twice daily. Previously it was up to 5 daily from Gatwick with fewer flights from Heathrow.
I can see this being reversed again in 2023. (when Heathrow slots may be needed for other services)