In order to do that pin correctly the extension housing, pan, valve body and rear servo lever have to come out. (it can be done without pulling the valve body, but not by many)
There is an O ring groove in the pin, and some just try to seal it without pulling it out, so if they don't pull the pan and rear housing they are not doing it right.
Here's the pin O ring in the first pic and where the pin sits in the trans in the second pic.