Yeah the article is a little rosy and overstating things by using words like carbon free which obviously isn't the case, but fta:

"Retrofitting a propeller plane with fuel cells and liquid-hydrogen tanks would result in a nearly 90 percent reduction in life-cycle emissions, compared to the original aircraft, according to the International Council on Clean Transportation (ICCT), a nonprofit think tank. That’s assuming the hydrogen is made using only renewable electricity —not with fossil fuels, the way the vast majority of hydrogen is produced today."

Battery powered commercial airplanes are a pipe dream right now, batteries are just too heavy for anything practical with flight. Solid state batteries might reduce it some but probably not enough. We'll still need some kind of mass long distance travel in the future. Once they're able to scale up renewable energy sources even more, hydrogen made with those sources could become an important storage medium for getting that energy to power planes or other things where batteries are impractical. So it makes sense to at least be exploring these technologies.

Even for right now natural gas has a higher energy to co2 ratio than other types of fuels, so it's possible there may even be a current efficiency boost, though I don't know that off the top of my head.

If every new technology was attacked saying, well it's not perfect right now so don't even bother trying, we wouldn't have electric cars or all sorts of other innovations. I agree with you on the article though, I hate when they say stuff like "look we have carbon free airplanes now" when obviously we don't.