Yes ... no
The additional oiljet onto the 5th gear gets relatively cool oil from the oil tank, direct from the filter. This opposed to the relatively hot oil coming from the sump that is being pumped back to the oil tank.
Reading this back, it is quite non-uderstandable.
There are two circuits:
1 starts from the oil tank, to pump, thorugh filter, and lubricates crankshaft, engine top end. This oil has passed through oil cooler and filter.
Then, there is the second circuit that gets oil from the sump and pumps it patrly back to the oil tank, and partly to other parts like the gearbox. Before this oil arrives in the oil tank, it passes through the oil cooler.
On the older XTs oil from the second circuit was directed to the jet for the 5th gear. As you say, this yet now gets oil from the 1st circuit.
As to how much this will help: yes :-)