The syntax for cache hint is as follows:
(1) cache[([pref_mem] [ttl:n] [updatable])] [scope:(session|user|vdb)]
So if user wants to use cache for specific scope (e.g. session) according to declared syntax it should be:
(2) cache scope:session

But using (2) teiid ignores the scope. What teiid accepts is:
cache(scope:session)

So I suggest to update (1) to:
cache[([pref_mem] [ttl:n] [updatable] [scope:(session|user|vdb)])]