[allocator.requirements] suggests that the moved-from state of an allocator may be unequal to its previous state. Such a move constructor would break most container implementations, which move-construct the embedded allocator along with a compressed pair. Even if a moved-from container is empty, it should still subsequently allocate from the same resource pool as it did before.

std::vector<int, pool> a(500, my_pool);
auto b = std::move(a); // b uses my_pool too.
a.resize(500); // should still use my_pool.