I had wondered whether folks would make an effort to build a parent trap… ;)
Intention signaling is one of those things that I had to think seriously about.
On the one hand, the game is playable without it, and you can learn through observation and repetition what the routines are and approximately how long they last (at least with enough certainty for the fraction of a second you need to escape). It's a little disappointing when someone spontaneously turns around and spots you, in the Nethack "rocks fall and you're not wearing a helmet" kind of run-ending way, but when you've just managed to duck around a corner, or weave in and out of rooms just avoiding detection, that same risk drives excitement.
Signaling intention just in time (i.e. as it changes) doesn't actually help avoid any of the "spontaneous detection" scenarios, and at best gives you visibility into where the NPC is pathfinding to. How useful that is may be a reasonable subject for debate, since it's a reasonable blind spot for me.
On the other hand, if NPC intentions were signaled in advance, it's a lot easier to know whether you're going to be safe before you even move. It's not an inherently bad thing, but it does replace hard-earned knowledge with free information, and reduces the challenge of the game substantially closer to "can I move around well?". Given that the game is only just compelling with its current balance of movement and discovery, I fear that adding signaling would lead to higher scores and broader appeal but lower satisfaction overall.
Always happy to entertain the discussion, though! :D