Don't get mad at me, but I note that you hypothesize no option whereby Nadal finishes with the most Majors. Let me fill in that gap.
I think what you say, and Kieran concurs with, is very probable: That Rafa makes a big push to defend the AO and win RG in 2023. However that goes, he may be done. He's going to have a new baby, and he's always said he wants to be home for that.
I also agree that, if Novak can, he will try hard to outlast Rafa by at least one. He has said as much. He wants to have the most toys when the music stops, and he's not even cagey about it.
One thing you don't allow for is that Novak may not play the coming AO, nor any of the next 3. Another is the conviction that Novak is fit and healthy and has a few more years in him. This is a truism of that last while, but not a surety. He is beginning to show the signs of age. In Rafa, the signs of age have always been physical, but in Roger, and, I would argue, Novak, they tend to be mental. As the windows close, the pressure mounts, and each opportunity seems more like one of the last. Of the 3, Rafa has shown he can withstand the pressure of "last opportunity." (2019 USO and 2022 AO.) Roger buckled at Wimbledon 2019 (sorry to bring that one up again,) and Novak buckled at OG and 2021 USO, with so much on the line. With the youngsters coming up, there is a chance that Rafa, given that, as Paul Annacone says, will be the favorite at RG even 8 years after he retires, may yet get #23 at RG, even if he doesn't defend the AO. Novak may not even play it. And, as the pressure mounts, and the competition starts to speak for itself, Novak might have a hard time adding to his total in 2023. What pressures on Novak if Rafa gets to 23 and he's still at 21?
Just saying that there is an argument that they could finish Nadal 23/24, Novak 21-22, Roger 20.