Update the fallback entry in the man page
"FallbackDir ipv4address:port" "FallbackDir ipv4address:dirport"
"DirAuthority [nickname] [flags] ipv4address:port" "DirAuthority [nickname] [flags] ipv4address:dirport"
And similarly for orport.
"The provided port value is a dirport; clients ignore this in favor of the specified "orport=" value." "Clients always use the orport. Relays prefer the dirport, but will use the orport in some circumstances."
Add something to the FallbackDir entry talking about how the DirPort is used by the checking script?