Uhhh double sided performance is determined by interleaving...
A single - single sided stick is probably not enough banks to pull off interleaving.
Double sided does essentially ensure you can interleave a single stick.
There's also node interleaving too, but I never messed with that, none of the bios'es allow for adjustment that one either as far as I know.

It interleaves the access to the banks of mem.
Each bank is probably 2 chips I'm guessing, whatever the bit width of the chips are.. needing equ to 64bit per stick.

2 sticks, single sided, in dual chan, likely perform the exact same as the dual sidded in the same setup.
But it is possible maybe interleaving improves as you add more banks past what you need to get it to work in the 1st place.