I am often adding details about amenities at public transport stops to the public_transport=platform way, e.g. wheelchair accessibility, information displays etc.
Consider the bus station on the picture I attached to this post (the bus stops at the train station of Sarnen OW in Switzerland). As you can see, there are a few seats for waiting passengers on the left, then there is also a digital departures board/information display indicating bus departures for all bus platforms you can see on the picture (yellow/blue screen on the very left).
Do I add e.g. departures_board=realtime (or bench=yes, shelter=yes etc.) to all of the ways representing individual bus stop platforms, even if there is no realtime departures board (bench, …) on the platforms themselves? Do I add bench=yes to the bus stop platforms even if the bench is not physically on the platform itself?
Generally I’d map the individual features themselves here, and certainly not on the bus stops. The actual location of seating matters to someone with limited mobility (whether through health issues or being encumbered with bags or a pushchair). If all are included in the area footprint of the bus station it is not hard to deduce that the bus station provides seating, a vending machine, rubbish bin etc.
I think you could and maybe you should do both: add the bench=yes, bin=yes tags and separately map benches and bins and whatever. This because redundancy could be helpful for different situations: knowing that a platform has a bench is useful for elderly, knowing where the bench exactly is is useful for visually impaired people.
But the platforms don’t have benches, unless I am missing something? It seems misleading to direct people to the platforms in the hope of being able to sit down, if the benches are in another part of the bus station.
My interpretation was that the “platforms” in the original query are the narrow raised areas (e.g. where the yellow bus is parked), which do not have benches. The benches you mention should certainly be mapped within the bus station, but look like part of a general waiting area rather than the platforms.
