It wouldn't matter in this case. Its usually 1 1500 line commit in a PR, or its a couple of commits but they aren't meaningful ("write large feature", "review updates", "wip", "merge branch X", etc)
Some people consider the PR the unit of work, not the commit. I don't really agree but I think its a reasonable way to do things if you are squashing the PR before merging. The problem is the size.
On the other hand, on a larger scale, it's often more about figuring out what PR caused something to break, rather than exactly which of the 100 WIP commits inside that PR was the exact cause.