Is LeaverBuster associated with Instant Feedback punishments?

A few months ago I got a 14 day suspension for intentional feeding, and ever since I got unbanned I've been reforming and didn't get any punishments, but today I accidentally left an AR URF match from beginning until the end (forgot that I accepted a match during queue and went away from pc).

Since I got a recent suspension, that makes my next punishment a permanent ban, but I didn't get punished for this like nothing happened. Why is that? Is the LeaverBuster associated with punishment tiers on my account or not at all? How does this work?