Its different. Those long deals typically had very low salary years tagged on that the player may never have played to artificially reduce the cap hit. Hence money would be paid to a player that was never accounted for in the cap calculation. For these deals all money paid is actually accounted for in the cap hit. It is just that the player defers some of the money which is discounted to its present value. (See my post #898 for a simple example.)
Jarvis' deal is a little different than the example I gave but the principle is the same. You take the three deferrals and calculate their present value. In this case, the savings on the cap is not so great because there are only three deferrals and the biggest one is for only one year. Spreading out the payments after the deal is over would lower the cap hit more.
For a player the biggest possible advantage comes through possible future tax savings. As
@Soundwave points out a guy like Draisaitl could save tax by having part of his salary deferred if he establishes residence in a low tax country after he retires. Jarvis for example could retire in a state with no income tax and save the 5.25% he would pay on the signing bonus as a resident of North Carolina. That alone would say him almost $800K in taxes.
This is fairly sophisticated stuff for a player. So it may not be something most want to think about.