I have to disagree with explanation :crazy:
I looked up before answering and I found:
Query plans are read-only reentrant structures that are shared by multiple users.
The explanation is about execution context (not the same as execution plan):
From a query plan, an execution context is derived.
Although execution contexts are reused, they are not reentrant (i.e., they are single-threaded).
It is all at the same page that is given for explanation (see 'Query plans and execution contexts')
[reused in not contested]