I agree that Tapas is one of the better platforms that highlights the diversity of comics (it's one of the reasons why it's my favorite platform), but it still doesn't change the fact that they asked for colored comics in vertical scroll format for the Creator Incubator. Hopefully, as Woobv said, there may be a possibility of other forms of comics/graphic novels for this section in the future (Sorry for bad English, also this is my first time using the Forum and I'm trying to learn all the settings haha)
(EDIT: There are a lot of book format webcomics out there that are mobile friendly as well)