The TK codeshares are curious. BRS-DUS and BRS-HAM are showng now, but as once-per-day rotations, the connections into the once-per-day TK flight to IST are either bad (hours stopover) or terrible (overnight stopover)
When I last looked, the annouced BRS-CDG codeshares weren't showing. As BRS-CDG is 3x daily, that migth make more sense for connections but until they're in and bookable, it's conjecture.
As somone who books BRS-FRA/MUC on the LH codeshares quite often, the inventory management needs to be carefully overseen, and married segment availabilty brought in. Sometimes entirely legit inventory changes when considered as a point-to-point airline (e.g. passengers flying just BRS-FRA) have a dramatic effect when attached as the first/last segment of a long interncontinental itin.