I know that the 486SX had its FPU disabled, maybe by binning 486 CPUs into those with and without functioning FPUs. But did Intel eventually make a 486SX revision without an FPU on the die?
Yes, Intel did make 486SX CPUs with no FPU on the die. You can see the difference in die shots, e.g. from this CPU-World.com thread: early 486SXs are nearly indistinguishable from 486DXs, but later 486SXs are simpler (the right-hand side has been reworked, and is missing the FPU which was in the lower-right-hand corner).
This is a 486DX:
This is an early 486SX, with a disabled FPU on-die:
This is a later 486SX, with no FPU on-die: