Why pedestrians don't have priority on shared paths and shared spaces

Every time a video of a cyclist and a pedestrian on a shared route appears online, the same comments flood in.

West Yorkshire Cycling
@wyorkscycling Round here a single ting on the bell is taken by most people to mean "there's a bike coming up behind you: if you keep going as you are I'm not going to hit you, but please don't suddenly step sideways without looking." This mostly works fine, unless of course the pedestrian is wearing headphones.
@TimWardCam ‘Most’ = ‘not all’. Awareness is still required, regardless of bells or horns.

@wyorkscycling Yes, I said "mostly".

I was wondering whether this was just a local convention or whether it's used elsewhere - single ting "be aware that I'm here, you don't have to do anything", full ring "I'd like to get past please, but you're occupying the entire width of the path, so it would be helpful if you would move".