Log filters cannot match against cache result code TCP_SWAPFAIL

When creating a log filter to match only transactions that would go upstream:

traffic_server[40661]: [LOG_FLUSH] WARNING: There were invalid values in the definition of filter upstream_requests only 3 out of 4 values will be used.

Removing TCP_SWAPFAIL from the match, resolves this warning. All documentation branches list 'TCP_SWAPFAIL' as a valid result code, so not sure whether this is a documentation or implementation issue.