That's always true on the PDP-11 and Vax, no matter what the OS, because the processor architecture (which has pre-increment and post-decrement instructions, but not their counterparts) makes anything but a downward-growing stack unmanageable.  In OSes without virtual memory like RSX-11[ABC], RT-11, and mini-Unix/LSX-11, what counts as the top naturally varies.

Dennis's compiler AFAIK was never extended to anything but the PDP-11, both as host and target.