Since the last patch that fixed the issue with sticky blocks I created a flying machine using honey blocks since they're easier to acquire, but for whatever reason observer pulses aren't being propagated through them as they would slime blocks, preventing the machine from engaging.

isn't that just because they're not solid blocks?

Unlike the slime block, the honey block does not carry a redstone signal because it is a transparent block.‌ [Java Edition only]

From the minecraft wiki. Seems like that's intended.