alt Hacker NewsI suspect that in this case "seaglider" is just REGENT's marketing name, rather than a term with broader uptake. All the places I'm seeing the name 'seaglider' used in this context look like REGENT's prospective customers.
The term is also being used for some underwater drones (see https://apl.uw.edu/project/project.php?id=seaglider and https://en.wikipedia.org/wiki/Seaglider).
Sure, it seems to be this Regent that wants to make "seaglider" a thing.
You can understand why they don't use "ekranoplan" as the marketing term. Its going to only be familiar to those who are into Soviet History, Aviation trivia or specific Sci-Fi.
And it's not going to bring small, modern, electric craft to mind.