The standard procedure on the Airbus is also to use the slew (plus / minus) buttons to set a position for IRS INIT, as opposed to punching in the numbers.
This in order to prevent gross entry errors from crew side. Which, especially if only longitude is inserted wrong, could go undetected by the IRS verification algorithms.
Further reading in the book reveals:
IRS are automatically initialized with the GPS position. However, the flight crew can override the automatic position initialization.
And there is no recommendation (*) to enter gate coordinates at all.
Without diving in too deep, I would like to underline any and all
vilas' repeated post about how non-adherence to manufacturer's S(uggested)OPs brings dire consequences, unforeseen by whoever believes they know better. Unfortunately.
(*) that's actually not 100% true, but I'd take the challenge to see the quote from OEM manuals, full, with the specific conditions when this would be the best practice.