I believe this post is referring to device-scoped memory barriers - also sometimes called fences - as opposed to execution barriers.

The former being a mechanism to ensure memory accesses follow a well defined order (e.g. it'd be bad if the memory accesses executed inside a critical section could be reordered before or after the lock and unlock calls).

The latter being a mechanism that ensures all threads (within some scope, perhaps all threads running on the "device") reach the same point in the program before any are allowed to proceed.