This has been going on for a looooong time. Old time intel 486 "SX" chips without math co-processors (floating point unit really) were originally 486 "DX" with

This has been going on for a looooong time. Old time intel 486 "SX" chips without math co-processors (floating point unit really) were originally 486 "DX" with either the co-processor disabled or which failed QA. At some point, they made actual SX without FPU built-in. The "stand alone" math co-processor you could add to an SX based system to gain h/w floating point was actually a full blown 486 dx CPU with a different pin layout (one extra pin) so it couldn't be used as CPU and could therefore be priced differently.