MSyntax Flag Definition & Invalid Flag Error

I had some frustrating moments in making flags work for a command using MSyntax. A part of it was my ignorance in reading the function detail, but the other one I am not sure is mentioned in docs. Here is what it says in the doc. for MSyntax::addFlag(const char* shortFlag, const char* longFlag, ......)

shortName  the string representing the short (< 4 character) version of the flag
longName   the string representing the int (> 3 character) version of the flag

=> Short flag name should always be < 4 characters.
=> I defined one flag name like this:  syntax.addFlag("-it", "-infType", MSyntax::kDouble);
and used it with my command like this: myCmd -infType 2 Maya gave me an error, "invalid flag -infType"!

Then I changed the flag long name from -infType to -influenceType it all worked fine. So I wonder there is a problem with defining a long flag name beginning with three lower case characters, followed by an upper case character.