Can’t say I’ve heard this…but I suppose it doesn’t surprise me either.
To answer your question - - since every present second proceeds immediately into the past, it is reasonable to say that all forgiveness is in the past.
However, since we can have difficulty in truly forgiving and putting things behind us, forgiveness can be ongoing so continually in the past and present and (hopefully) in the future.
As to the matter of how we pray the Our Father,** I think that the petition really applies to all periods - past, present and future. ** We are petitioning to be treated by our Lord in the same manner that we have treated others - that we ARE treating others and how we intend to treat others in the future…
Just some thoughts.
Peace
James