I agree.

When you have a large PR like this, here's how I like to get it reviewed.

1. Give reviewers sometime to become familiar with the PR. They might not understand all parts of it, but they should have at least a cursory understanding of the PR.

2. Have a meeting where the PR is explained in front of the group of reviewers. The reviewers will understand the PR better and they can ask questions in realtime.

3. Let folks review the PR after the meeting in case they spot anything else, or think of additional questions.

Most of the time PR review is done asynchronously, but doing most of the review in the meeting can also be a decent team building exercise.