There are at least two distinct types of these jump starter packs. On has a Sealed Lead Acid Battery. Like emergency lights, computer backup-ups and the like. Those are a brute force jump start like from another vehicle. Hook it up, wait a few seconds and try to crank. A battery charger with a Jump Start feature would also be like that.
Then there are the new, smaller, lighter ones based on Li-On batteries like power tools. They seem to work more like using a battery charger without jump start, or using a similar pack to recharge a phone or tablet. Hook it up and wait a few minutes for the pack to "charge" the vehicle's battery vs. "jump" it.
We have one of the older type, and it definitely works. Since gotten two of the new type and haven't had the occasion to try either. I do know, they come with a "lighter plug" and battery terminal clip leads. I'm old school enough to want to use the battery clips. Can't imaging much of a Charge or Boost passing through the "power outlets" with 10A fuses...