22B-
Again, I think it was quite clear that some people misinterpreted 80 in the original post to be the subtest score not the percentile ranking. That has been clarified. However, it is also important to note that other people, beyond the original poster, do read these threads. A person coming along and reading that there is a 40, 50 or 60 point difference in subtest scores should MOST DEFINITELY take that as an INDICATION that something else might be going on and investigate further.
Indication by definition, does not state there is a problem. It is a sign of a potential problem. Sometimes a lump is cancer, sometimes it is a pimple. The lump is an indication of something happening.
Just as you cannot make a diagnosis from an indication on the WISC, nor should you disregard the information completely. Perhaps it's an indication of perfectionism, a learning disability, a visual tracking issue, an attitude problem or a lack of sleep that day. Regardless, if you are going to bother to test, you should also bother to consider the information presented.
As to the OP, I do not think a discrepancy of that amount would qualify as a true learning disability. Whether or not it meets Webb's "functional" learning disability definition, well you'd need further information. Only you know your child's personality and mood on that day and whether or not it's reliable data or not.