The Law of Exclusivity already contains an opt-out for atomic operations, so they are allowed to result in overlapping accesses just like reads can (although - importantly - they are only allowed to overlap with other atomic operations, just as nonatomic reads may only overlap with other nonatomic reads):
To resolve this problem, we propose to introduce the concept of atomic access, and to amend the Law of Exclusivity as follows:
Two accesses to the same variable aren't allowed to overlap unless both accesses are reads or both accesses are atomic.