Well, to consider bending, go back to fundammentals: You have to have a lever arm, a force on that lever arm, and a "pivot point" (a point where the object to be bent will actually start its turn).
So, start with an ideal case: the bolt is in perfectly "hard/rigid concrete" and cannot "wiggle" in the hole (it is cast in place or fastened with epoxy filler in the hole or inserted into a very tight hole, the load is applied in pure shear (in parallel to the surface of the concrete), and that load is applied very close to the surface of the concrete.
What can bend? How can it bend? It's simply not possible.
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Real world: The hole is oversized or the concrete around the cast-in-place bolt deforms, the epoxy yields a little. The baseplate is pulled sideways and "up" away from the concrete (which yields a little bit) and thus there is a bending action on the baseplate. This pries up one half of the bolts on the "high side", and bends the bolts closest to the bend in the baseplate on the "low side".
Real world, the loads are applied up above the surface of the concrete, and those loads have a vertical component: usually much smaller than the shear component, but it is there. The baseplate holes are larger than the bolts = which allows the bolt to yield sideways a little bit, and so the bolt will be able to bend at the surface of the concrete: it can't be kept perfectly vertical.
But it is the prying action of a "flexible" baseplate in soft (or cracking) concrete that will cause the most problems.
With a sufficiently rigid baseplate, the yielding (failure) is usually in pulling the bolts up out of a hole out of their anchor (that, in this case, is resisted because the bolts are through the concrete slab), or in stripping the threads and pulling through the bolts on the high side.
Then the sign or post fails by fallin down, thus bending the bolts on the low (downwind) side. Yes, they bent, but after the initial failure.