> Асинхронно можно выполнять чтение, но не запись, как я понимаю

Нет, всё верно. Операции чтения выполняются всегда сразу (блокируют процесс), а запись может быть отложена.

"A process issuing a read request is typically unable to proceed until that request completes and the data is available, so such requests are seen as synchronous. A write operation, instead, can complete at some later time; the initiating process doesn't usually care when that write actually happens. So it is common to prioritize reads over writes, but not to the point that writes are starved."