Does it?
According to my data stall depends on AoA, nothing else (at least as
long as the wing is not swept). The advantage of a forward-swept weing
is that its unstalled tip is not affected by the turbulence from a
staled inner wing.


See "Fundamentals of Sailplane Design," page 42 in the English
translation by Milgram.

"Aspect ratio and wing taper have a pronounced effect on circulation
and lift distribution.... Fig. 58 shows the influence of taper on
lift distribution. The sharp increase in lift coefficient observed
near the tip of a highly tapered wing indicates that the stall will
develop first in this region. This is why highly tapered wings are
often associated with poor stall characteristics. Rectangular and
moderately tapered wings present less of a problem in this respect."

As far as I can see, there's no explanation there for why this
happens. Stinton, in "The Design of the Aeroplane," presents a
graphical method for estimating lift coefficient on a
non-constant-chord wing, but doesn't explain why taper affects lift
coefficient distribution either.

Sweep isn't discussed by Thomas, but Stinton says (p. 146)

"Swept back wings have two disadvantages at increased angles of attack
and reduced speeds:
- Wing boundary layers tend to drift outboard, assisted by the
spanwise component of flow in fig. 4.13a, which causes them to thicken
and separate prematurely at the tips.
- Sweep staggers the vortices shed across the span, so that those
shed inboard are ahead of those shed further out. This causes
increased upwash ahead of the tip, with a corresponding increase in
tip angle of attack, accompanied by premature peaking of the lift
coefficient.

The overall result is that swept back wing tips stall before the
root... Forward sweep avoids premature tip stall, because the root
stalls first. However, forward sweep has an adverse effect upon
directional stability, and larger fin area is needed than with
sweepback."

If you look at a beginner's hang glider on the launch ramp, sighting
along the leading edge while the wing is developing lift in the wind,
you'll see enormous amounts of wing twist, with the tip clearly at a
negative angle of incidence to the flow but still developing lift!
This is the clearest visualization I've come across of the way that
the "tip" vortices shed inboard result in a higher local AOA on the
outboard portions of a swept wing: the tip is at a negative incidence,
but a positive AOA. With forward sweep, the reverse could happen: the
center section might have a negative angle of incidence but a positive
AOA.

Mat seems to be seeing the two effects offsetting each other: the
forward sweep of his wing (looks like a straight leading edge, forward
swept trailing edge, which is a forward swept wing) tends to make the
root stall first, while the taper ratio would tend to make the tip
stall first. It looks like the sweep is winning.

However, I agree that taper ratio and sweep alone don't seem to be
enough to predict tip-stall behavior, which will also depend on wing
twist and the airfoil used at the root vs tip.

I clearly need to fly more and spend less time with these books!