> by definition you have flat memory.

No, not at all.

It would be more accurate to say:

"by definition you can have flat memory, if you want, but you don't have to."

But everybody wanted to.

In x86-32 you can absolutely have segments if you want. In practice, for an easier but far more insecure life, everyone opted for "one big segment pls kthxbye".

The question is understandable because EMM/EMS use protected mode in a limited way.

In fact, 386 protected mode could still make use of memory segmentation, with 32-bit segment registers being an upgrade from the 286 protected mode.

But there has been no production OS that continued to use segmentation once 386 mode made 32-bit addressing so easy. In large part because Unix could be ported from flat memory models such as VAX, and m68k.

Therefore, since CP/M-386 is derived from CP/M-68K, it seems straightforward that a flat 32-bit memory model is employed.