Have to correct: It's not the elliptical wing tips which stall first, it's the tapered and swept wing panels. To make it blatantly obvious, here's how it looks if this panel has even 6 degrees washout, progressively from the square center panel to the elliptical wingtips. At the same time the airfoil is tapered from NACA 2215 to 2206, as before.

Nearly no lift at the wing tips (look at the orange grid for induced drag) and laminar flow (the red transition line) for aoa=6. One more degree of aoa before stall begins: aoa=11. Very little lift at the wing tips and mostly laminar flow. But strange things happen, there's much viscous drag (the pink grid) in the middle of the tapered wing panels. Like before, the transition line comes close to the leading edge near the wing tips.

At one more degree aoa (12) the tapered wing panel stalls except a small outer part. Again one more degree aoa (13) lets the whole panel stall, and even one more (14) also the wing tips. The square center section is still unaffected. Only at aoa=17 the center panel stalls all at once.