Small note: As far as i know opentopomap is currently not maintained and does not render new tiles (only provides old cached tiles). See OpenTopoMap Serverwartung (german, but you can use the translate button)
With regard to the path mentioned: I think the tagging with trail_visibility=no and ‘expert’-sac_scale is fine, but we should make sure that such tagging is regarded in more map styles. It is indeed somewhat unfortunate that a route that is already tagged as not visible is rendered on the standard map style.