If A, B, C, and D are all on gigabit on the same switch, if A and B are using their full gigabit to talk to each other, C could get significantly different bandwidths if it tries to talk to A vs. D. Is that homogeneous? Depends on how you define it but "no" is probably the more useful answer.

(There's a couple of other possible outcomes, like the switch prioritizes C, but then the A<->B link sees variable bandwidth over time, another type of inhomogeneity. One way or another something is going to give.)