Not really. That makes the time at which the unsubscriptions happen look more random, but it still needs that delivery to many yahoo users failed "5 emails ago", which (unless the list had a large gap between mails then) should be relatively uncommon.

Many unsubscriptions from the same provider look like yahoo bounced many emails at that point (an email rejected because it was considered suspicious, throttling, etc.) which made mailman think all yahoo users failed, and thus ultimately unsubscribe them all at the same time (still, if it was content-related, the individual mail check should have prevented the unsubscription...).