bicycle=dismount does mean that cycling is not allowed, and that cyclists should dismount and wheel their bikes. That precisely reflects what’s shown on that streetview image (which presumably is what’s still there? I last visited this area last year, and it’s what I remember being there.)

bicycle=no is documented as meaning the same, but also has a potential other meaning of bicycles being disallowed entirely, even when wheeled. So to avoid confusion it makes sense to me to tag as bicycle=dismount.

Tagging as bicycle=dismount also makes the reasoning behind the tagging very clear to any future surveyors, as it obviously matches the ‘cyclists dismount’ signage.