procps installs locale in /share (not /usr/share)
The APKBUILD for procps has —prefix=/ and its locale gets installed to /share. —docdir and —mandir is explicitly set to /usr/share/{doc,man}, so it seems like —localedir ought to also be set to point into /usr.
(from redmine: issue id 6577, created on 2016-12-23)