The "Houthis" (Ansarallah) didn't shoot at ships without provocation. They did it as a response to the genocide in Gaza, out of solidarity, to implement a blockade. They said as much, and the article explains this.

The author seems concerned that if the people [...] are labeled terrorists, they might receive less aid, even though aid exemptions have been added?

First of all, the author is not (only, primarily) concerned with aid, but rather trade.

Secondly, and the article explains that but maybe not clearly enough, but sanctions cause lots of companies to stop all dealings with the sanctioned entity, despite humanitarian exceptions. This causes massive friction not just for trade, but also for humanitarian aid, as the humanitarian aid groups need to contract out e.g. logistics to companies, and they need to be able to do payments. Sanctions always cause collateral damage in this way, because they create lots of paperwork and legal grey areas, and companies do not want to deal with this.

Potentially receiving less aid seems like a reasonable consequence

You are aware that thanks to the previous Saudi (and US backed) blockade and US sanctions on Yemen, hundreds of thousands of people died, mostly due to starvation and such, and most of them children. Starving children may very well be the consequence of the US's actions. Do you really think that's fucking reasonable?