Two hypotheses instead of one, and the oracle that could not tell them apart

sceLibcMspaceMalloc was answered with zero because D125 says so, and nothing was compared against it. The reason nothing was compared is that the alternative could not be said: the policy had StubReturn for what a function answers and StubWrite for a region delivered through an argument, and only the second could produce a region - the wrong one for a function that returns a pointer.

They are one concept. StubRegion { via, bytes } with Delivery::{Argument(u8), Return}, and the service decides delivery when it resolves the base (D300). "Answer with a region" needed no new diagnostic either: ORBISTOUN_MAP plus ORBISTOUN_RETURN at the mapped base is exactly that, which is the same two-axes-together shape D283 was about.

The loop now runs both and keeps whichever reaches further. Pointed at the same title:

*** sceLibcMspaceMalloc answered the code the guest followed;
    zero reaches 25 against 13, and did not fault

It kept zero, and the reason is the finding. Zero already reached every import the run makes and produced no fault at all, so a region had nothing to improve on. The comparison ran and the oracle had no headroom to express a difference (D301).

FURTHER answers "did the guest get past something" - the right question while a wall exists and no question at all once one does not. Two answers that both clear the last wall are indistinguishable to it however different they are to the guest.

What would separate them is 035-libc, which grades an allocator against a spec. That is Evidence::ConformanceCheck - which every region-bearing patch already declares it needs and nothing enforces. It is a label, not a gate, and this is the case that shows why the gate has to exist before any of this runs unattended.