I'm not sure there's a minimum per se, but I think it's somewhat unusual to have so many points around a corner like this. Might be best to ask in the OSM discord! https://discord.gg/openstreetmap

For what it's worth, this change revealed a very subtle bug in Valhalla and I was able to submit a patch to fix it :): https://github.com/valhalla/valhalla/pull/5529