Hi
pton18 and welcome to FlyerTalk!
It is a long-term known issue that ITA Matrix would show non-existent phantom availability for TK flights.
In this case the cheapest available fare bucket for TK 8 on July 23 is T and for TK 187 on August 8 is S which means that V and L fare buckets are not available for the respective flights.
I wouldn't trust ITA Matrix when it comes to TK availability at all.