AFAIK, FreeBSD has been doing transparent superpages for decades (I think it was implemented in 2002 for x86 [1], and 2014 for arm [2]) and I don't know of any real issues with it? (I'm sure you could build a test case where it thrashes and causes trouble) Not sure why Linux wouldn't do the same??
[1] https://www.usenix.org/legacy/events/osdi02/tech/full_papers...
[2] https://www.bsdcan.org/2014/schedule/attachments/281_2014_ar...