ST staff have indicated informally on this forum, this year, that Smart Lighting is a legacy app whose use would be deprecated in future, and engaged in discussion about what functionality Automations (Routines) still required to be able to replace Smart Lighting. So this titbit could represent a relatively recent change in intention. It could also be wrong. As could the previous information. We still don’t really know for sure.
While I personally have always tried to convey an air of uncertainty, perhaps unsuccessfully, I have always regarded migrating from Smart Lighting to Automations/Routines or the Rules API to be reasonable advice given the best information available at the time.
I also advise it because of Smart Lighting’s idiosyncratic handling of multiple motion sensors and toggles and the inevitable question mark over what would happen if an attempt was made to replicate Smart Lighting using the Rules API. Would/should these quirks be replicated? Also how will the transition away from legacy features like button numbers and child devices be handled?
The real danger, as I see it, is in users not being