But crossing here, through the traffic islands *is* prohibited, by the traffic rules valid in this country, where you are not allowed to cross a motor road anywhere you want (and I suspect there are additional rules about doing so on or near crossroads, but maybe I'm mistaken there).

If a routing app sends you through here, it's buggy. The proper routing for foot traffic is, like I already mentioned, to go a few meters to the north and to cross Podlučinského using a marked crossing.

IMHO these ways should be tagged according to the reality on the ground, not according to what some particular router would do with the data.

See also https://wiki.openstreetmap.org/wiki/Tagging_for_the_router