with rpi-swap, what does sdm's swap=nnn do?

[tinker2much]

I read a bit about the new rpi-swap here. It seems like it sets the optimal amount of swap automatically. If so, what does the sdm swap=nnnn setting do now?

[gitbls]

I have a TODO item to sort out swap=nnn WRT Trixie's rpi-swap, but it's not there yet.