[koliber]

There is a sign in Germany that indicated "must turn right".

https://en.wikipedia.org/wiki/Road_signs_in_Germany#/media/F...

Combine that with a stop sign to force a stop and yield.

It feels like this would solve the situation without the need for traffic lights. I'm sure I'm missing something though.

[RugnirViking]

From what I have gathered, the reason is that all sides of a junction must have traffic lights or none. Because traffic lights are needed at the other entrances, this one is installed to comply.