Backtracking works as expected
?- call(member(X,[1,2,3])). X = 1 ; X = 2 ; X = 3.
The text should probably be changed from
Note that clauses may have variables as subclauses, which is identical to call/1.
Note that clauses may have variables as goals. And such a variable X is identical to
There was a specific question on this at Discourse: