Rule_Str = not a string, but tied to strength!
Rule_Int = not an integer, but tied to intelligence!
/sarcasm
If you peruse the source code,
https://github.com/EQEmu/Server/blob.../rulesys.h#L52 you'll see that the "Int" suffix is leveraged in rules to parse integer-based (numeric) rule values. There is no Rule_Str, and hopefully it will help with understanding this conversation.