Negative behavior can not block champion mastery 6 & 7

You can be toxic and be very skilled at a champion. Riot preventing earning those levels because of negative behavior means that mastery level 6 & 7 does not represent skill.

I earned S+ on some champs and it shows my highest season rating is A

I also earned S+ to get a champion to level 7 which shows I'm skilled at that champion but negative behavior blocked it. Does not make sense.

I agree it should block earning loot keys and boxes thats fine but not representing skill