Personally, if I see a review that is >10 files that isn't explicitly a "Refactor" review, or I've been prepped ahead of time, it's probably going to take a long time to get the review out, because there are so many things to iterate on. I also have to block out a lot of time to even do the singular review, because it is so long and there is so much cognitive load to carry with it.
Smaller reviews are almost always better. If a review really can't be "completed" in a single PR, then I've also suggested 1/x reviews where bones are placed but gated under an FSS or something similar. This prevents code that shouldn't be run from being run until the whole feature (even if small) is complete, and lets the reviews focus on independent parts.
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Essentially, I'm saying I disagree with you placing the "error" on the senior developers in this scenario. Burdening someone with insanely large reviews is the err of the submitter.