(j3.2006) Does anybody remember why WAIT is OK for nonexistent units?

[Van Snyder]

Does anybody remember why WAIT is allowed for nonexistent units?

The only reason I can think of is that CLOSE is allowed for nonexistent
units, and CLOSE does a wait operation.  But it would be trivial to say
that CLOSE does a wait operation iff the unit exists and is connected to
a file for asynchronous operation.

Is there another reason to allow WAIT for nonexistent units?