Async PR reviews are an absolute nightmare. Very simple conversations take forever. Reviewers will see something that’s not an actual problem, just something they are confused about and leave a comment rather than approve, and then your PR is blocked for a minimum of most of the day while you want for them to see your response. I just approve any PR that doesn’t have obvious issues now.

Meanwhile if you have a call to discuss it or do it in person, you can rapidly answer any questions and get the reviewer to fully understand what they are looking at.