We did PR's on documentation files at my last place, it worked but it was more painful than getting reviews for code PR's. Tickets work because they can be reasoned about, shoved aside, brought back into the limelight, updated, other tickets can easily be related to them as more information is discovered, etc.

Overall the comments on this page fall into 2 camps, people who've tried it all and found what works is discipline and those who are still trying it all.