Hi and welcome to the forum Oil level too high?
Have you looked inside the pipe from airbox to turbo? The 60mmish diameter hose, could be start of turbo seals expiring if excessively oily in there.
Doesnt look good, next id check intercooler to see how oily , possible seals are going, endfloat can be same on good working turbo unit, id also check compressions to assert facts before replacing anything. Good luck
Id say yes, I had a non turbo subaru legacy did exactly same as you described when sitting idling in traffic, it had worn piston rings but had near 200k on clock. Id do cylinder compression test next.
I had a zafira gsi,. My other problem turned out to be stem seals.