No.
You are assuming that all leavers do so intentionally. This is not the case.
There are many reasons why someone can unintentionally disconnect that are beyond the player’s control, from unscheduled Internet Service Provider interruptions to power blackouts, hardware failures, & more.
It’s already unfair that those who leave unintentionally get treated the same as those who intentionally disconnect. There is no need to make the penalty worse.
In fact, there would be no need for a leaver penalty at all if Blizzard would just add backfill to Competitive already.