There are many different reasons for storytelling. Alice Oseman herself is a part of the queer community, and while Heartstopper may not be strictly "Own Voices", it's her attempt to show queer characters truthfully, rather than through an idealized, fantastic lens.
I've read and watched the story faithfully since I first learned of it, and I believe that Heartstopper is one of the most honest portrayals currently available.
Several actors in the Netflix adaptation (including the two protagonists) are also queer, though they may not have known it when filming began. Working on Heartstopper might just have helped them to discover their own identities, as it has for numerous fans.