Does mastery rank 6 & 7 create toxic behavior?

Lately i have been trying to reach mastery rank 7 with a bunch of my favorite characters. While doing this i have noticed a lot of things with myself and other players. For starts I find myself wanting to quit a game if I know i cannot achieve an s or higher. It seems some people afk at the first sign they cannot get a S. Its happend alot lately like if someone dies twice in lane they just quit. I stick the games out even when i do not want to but from knowing that i cannot achieve the whole goal of why i started that game does get under my skin and i noticed it effecting how i play. I always try to knock it off and i stick it out as best as possible. From there it seems getting a lot of kills helps your scores which is obvious but i find my self poaching kills that other wise would have been obtained by someone else. Granted i haven't seen any difference in kill poaching lately but I does add a new motive too. Also it seems playing champions off roles make for easier S's. I have played champs in odd ways (AD is the only truth) and did average but still obtained a S. So i have noticed a lot of other people doing this and the champs (granted the people know the champ well enough that they do well enough not to be considered heavy).

Has anyone else done, felt, or noticed these things , lemme know because i am honestly interested in this.