I think you're right with Dwarf Sag, but,,,,,,,Dwarf.Dwarf sag, maybe? Whatever they are, they look great! Fast-growing carpet plants are kind of like the holy grail in this hobby!
I got these as seeds from fleabay. I placed some on wet substrate soil in a dish but couldn't get them sprouting. I then placed some kitchen roll over them that helped keep them wet and in place and away they went, but only slowly.
When they were around 6mm high I tried to take them out of the kitchen roll but as the roots were underneath and the leaves were on top all I could do was tear bits of the roll off with the plants attached and then put them in the tank like that with a bit more substrate over them.
I love them but I think I'll move them.