You missed a link to the area you are asking about. But generally: no, don’t add “virtual” crossings. A good router can assume where it is possible to cross a highway. We should rather tag where that is not possible: e. g. a dual carriage way needs to be mapped as two separate ways. Where there is a fence between road and sidewalk the sidewalk should be mapped separately, etc.
In particular, virtual crossing do not exist on the ground, but are personal opinions, so they violate the “map only what is on the ground” and " do not tag for the renderer" principles. A router is considered a renderer, in this respect. Some things that don’t exist on the ground, like administrative boundaries, are mappable, but they still have to be more than a personal judgement.
Incidentally, this may be another case where routers have to be country aware. In the UK, you can cross a road anywhere that it safe to do so, but I believe that, in the USA, crossing at other than an official crossing point constitutes the misdemeanour of jay walking.
I tested a walking route in maps.me where there were separate sidewalks mapped without connections and it routed the user into the street instead. If it is against the rules to map connections to make sidewalk routing possible, does that mean we shouldn’t have separately mapped sidewalks except in special cases?
It’s a controversial topic. While I personally try to avoid separately mapped sidewalks there are also many mappers that promote them. I’d say it’s good style to not change what other mappers have already done as there is no consensus in the community.
If sidewalks are mapped separately one needs to take care that routing works correctly at all intersections. Where roads, driveways or footways intersect they need to be properly connected to both road and sidewalk. If that is not done a router like mapsme has no way to determine where a pedestrian can cross.