I think you guys are ignoring the fact that the original floor had glue holding all the tongues and groves together. How will the old tongue come out of the groove without damaging the adjacent board? And how will the groove on the board you take out come loose from the tongue on the adjacent board.
I have a client with the same type floor who wants individual boards replaced. I just don’t see how it can be done where the edges will ever stay together. Maybe if it was laid straight on the slab, then everything could be glued down and glued together. But with that mat underneath, the boards have a little movement.
I’m wondering if the original poster ever tried what was suggested.