Yah, you're right. Quoting from the review: "we’ve yet to find a battery / cable that can charge the console faster than it drains." So it's possible and likely that someone will make a capable pack at some point.
On the positive side, plugging a powerbank into the Switch causes the console to recharge faster than it depletes its own battery even in a stress test scenario with brightness and volume maxed. [1]
http://www.eurogamer.net/articles/digitalfoundry-2017-ninten...
I expect we'll see 5A+ power packs in the future which will handle it easily.
It charges my XPS 9350 just fine, so it should do the Switch no worries.