From mek on the CL [1] that inspired this:

"I'm not sure I agree that getting rid of feature-specific OWNERS files if a net benefit, even if the feature specific OWNERS files don't functionally do something. There is still value in documenting who feature OWNERS actually are. Ideally feature specific mojom files would require both security and feature OWNERS review imho, but since OWNERS files can express that, the next best thing is to at least document who the feature OWNERS are (okay, in most cases it will be pretty hard to change a feature specific mojom file without also changing at least one other non-mojom file where that other file would still trigger feature OWNERS, but for things like mojom_traits that's not always the case).

Of course this file is a weird case in that apparently there aren't any owners for common/page..."

So it seems like maybe the per-file rules are here to stay for now, unless we figure out the semantics for implementing something like !important.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/939206/1/third_party/WebKit/public/mojom/page/OWNERS#2

Perhaps we'll revisit in the future.