CjMalone
I walk this every day.

In reality, after SS100 everyone rides on the service road (https://www.openstreetmap.org/way/42517347), not this section of "Shanklin to Wroxall Cyclepath" (which should probably be a highway=footway). I don't know what the legal access of this is though.

I don't know about NCN23, but Sunshine Trail used to have a sign (https://www.openstreetmap.org/node/4009632024) at the top of the stairs opposite. So the official route is up them.

I've seen people awkwardly jump the kerb here (https://www.openstreetmap.org/node/530897535) onto the sidewalk, then up the steps.

I don't know if OSM wants a unmarked crossing, there, or here, or the relation adjusting to use the zebra crossing just to the north.