Every rear-end accident I've ever been aware of at a stop sign would have happened whether the person in front stopped for 2 seconds, 5 seconds, or 7 seconds. They were all due to the person in the back not paying attention and not driving safely. Whether the person in the front did a slow 5 second rolling stop or a 5-7 second full stop has never been relevant.

I'm unaware of anyone I know around here ever getting rear-ended because someone stopped at a stop sign. Granted, the culture here is to actually stop at each stop sign, so, you know, it's expected that people will actually stop and not just assumed that they're going to roll through.