The point of the second look left factors in the uncertainty that creeps in when you look right and spend time on the decision making process. It doesn’t feel like much but a lot can and does at times happen in that moment. You also lose some focus on what was happening on the left side because you need to shift your attention to the right. It’s like a quick refresh because once the decision is made to cross you can’t always take it back. As for you assessment of it being redundant I get where you are coming from but it’s more of a percentage of effectiveness thing. The first look left might only add another 5-10% to the the accuracy but that’s where most the errors can be prevented