It's a Tapas Premium, not Webtoons x )
And i'm pretty sure both of them are very possessive of their exclusive webcomics.
Not only the comic is published on a different platform, but also follows the same paid model on these two platforms.
Like... even WebComicsApp only allows the paid model if you sign an exclusivity deal with them, which it's clearly not an exclusive with the Tapas version still available. Not yet, at least...
I hope the artist is very aware of this cuz otherwise this looks shady as heck and i worry for them lol