I purchased a T bar style short throw shifter (which i'm happy with) now it has a button on the side which works but seems to have no effect. I had a good look at the old shifter(original) and there's a plate between the tunnel and the shifter mount. Am I correct in assuming this plates job is like a gate to prevent selecting reverse by means of needing to push shifter down to clear this plate(not fitted with new shifter). Anyway I can select all gears without pushing the button which took a bit of getting used to but works fine.
Anyway is this correct or am I missing something?.

i dont have a button but ive got a Scat dragfast in mine and it will not slect reverse unless you pull up this lever. is it possible you have something missing? is your shifter a berg styled one?
Steven