I would agree without even the caveat of the maintainer being busy. When a maintainer receives a massive changeset they have to then recover why the task was taken on in the first place and understand any decisions to get to the same outcome presented in the changeset provided. The more logical complexity that this change represents whether it is 3 lines or 3000 lines still needs to be understood by the reviewer as not breaking the rest of the system and equally can be 'massive.' The further you get from an N+1 change into a N+5 or N+6 change is where you get into situations where a N+3 change is flawed based on the rest of the system and invalidates large parts of the changeset, and that doesn't resolve all the issues or concerns.

I think a lot of people forget that changesets are sometimes not the most straightforward way to express ideas. They (including myself) also forget that while you are working with a change in front of you it's obvious but in one month it could be opaque. A maintainer is often giving you the perspective of you a month later who built on this system you changed.