the markers don't mean squat unless you have a means to verify it.
transitioning from correlated to causal is a big canyon.
process some animals and go see the carcasses. it's still the only way.
also, take notice of marbling type and be aware of the fact there is something called cream marbling or something. can't quite remember the name.
also, make sure you look at carcasses hung the same amount of hours.
or, enroll in meat science at one of the places verifying this industry.