That being said for Germany, traffic_sign=none has been discussed for unsignposted markings-only situations. I don’t read German, so someone can update me on any further discussions. Fahrradinfrastruktur Tagging - Realität und Fragen
Markings being a traffic sign is a legal technicality. Despite the Vienna Convention being being named as signs, markings are in another chapter similar to the titled signals. TSRGD regulates signals and other lights, but they won’t be said as signs. traffic_sign= has added factor of being established in OSM for id. As further said, they are country-dependent.
Notably, “stop sign” and “give-way sign” are defined as the “upright sign” only. Interestingly, a matrix sign is defined as a “light signal”. The Traffic Signs Regulations and General Directions 2016