Mongomirror documentation of the process arguements does not match the help output for the binary itself.
Not sure whether this should be a fix to the documentation or mongomirror itself.
Technically, mongomirror does accept sslAllowInvalidHostname and sslAllowInvalidCertificates as arguments even though they aren't mentioned in the help output. (Note: I haven't actually tested that they work)
tlsInsecure is listed in the binary help output (and definitely does work) but is not mentioned in the documentation.