I think there's valuable use-cases for both approaches. I don't work at JB so I'm just guessing here, but I think they have limited resources and had to choose one technology to focus on. For them, I would guess canvas / multiplatform makes sense, because Compose HTML is already working enough that you can do stuff with it even if they never work on it again (there are enough escape hatches you can essentially put anything into the DOM you want even if they don't support it yet). Meanwhile, multiplatform across all targets would let JB and Kotlin compete directly in the Flutter usecase (which, well, I haven't checked recently, but has been very popular for startups).