The exaggerated SR gains with win streaking is extremely difficult to trigger now, unlike season 1. For a while I thought it was gone completely, but then I gathered some data and saw some believable forum posts. I talk about it (with links to data) in How Competitive Skill Rating Works - Season 17 → Win Streak Bonus / Loss Streak Penalty.
It is difficult to know the exact mechanism that causes SR bonuses with win streaking, but “then we assume mmr can become uncertain if a player improves in play quality drastically” and SR chases the new MMR is a reasonable hypothesis.