Biff wrote...
Who says?

From Excel help:

If an array or reference argument contains text, logical values, or empty
cells, those values are ignored; however, cells with the value zero are
included.

I would think that the IF() falls into the "reference argument [that]
contains text" category but apparently not.
....

References are *EXCLUSIVELY* ranges an 3D references. The result of
your IF function call when A13 = "x" is A14, a range reference, but
when A13 < "x" it's "", which isn't a reference of any kind. Try

=ISREF(IF(A13="x",A14,""))