That's true. From a technical standpoint a closer example would be Jac Goudsmit's Propeddle project, or its predecessor, the Propeller-6502 hybrid made by Dennis Ferron. There's actually a long tradition of using the Propeller as the equivalent of custom silicon in such projects before people started doing the same with ARM.
I think the only thing that really holds the original Propeller back in such projects is that while the Propeller is fast, it's going to take a few cycles to interface the 6502 bus whatever you do. The Propeller runs at 20 MIPS per cog, which can easily bit-bang the bus when the 6502's running at 1 megahertz or so. But if the 6502 is running at 16 megahertz then it's not going to be able to keep up without some external decoding logic and throwing in a wait state via the 6502 RDY pin.
The newer Propeller 2 would have no such constraints, but it's also a more complex chip that you can't get in a 40-pin DIP.
I think the only thing that really holds the original Propeller back in such projects is that while the Propeller is fast, it's going to take a few cycles to interface the 6502 bus whatever you do. The Propeller runs at 20 MIPS per cog, which can easily bit-bang the bus when the 6502's running at 1 megahertz or so. But if the 6502 is running at 16 megahertz then it's not going to be able to keep up without some external decoding logic and throwing in a wait state via the 6502 RDY pin.
The newer Propeller 2 would have no such constraints, but it's also a more complex chip that you can't get in a 40-pin DIP.