Do you anticipate any temporal quantization or aliasing problems with tracking time as (presumably) integer picoseconds in simulation for systems with multiple clock rates? It seems like there could be edge cases where sim would consider activities simultaneous which would be ordered in hardware, depending on the usefulness of that distinction at the sub-picosecond scale.
The sim models multiple clock domains, multiple clock sources (the xtal component), and multiple clock converters (the PLL component). It allows for the cost of the handshaking required to cross domain boundaries.
The sim does not model skewed clock strategies such as appeared in the P4 and some other barn-burner chips. It could, but the hardware guys are not expecting to use such techniques any time soon, and so we wouldn’t know what to specify.