Arch Linux Wiki has said explicitly that they don't have any
responsibilities about what a package in AUR does and they also say that
it's mandatory to read and understand PKGBUILD (or any other file or
patch that a installation requires) before installing any package.
But when a package gets updated and those who have enabled notifications
want to update the package, they should (I would say everyone must)
click on package page, view changes, and click on latest commit to see
what has changed.
So appending latest commit link "helps" and "encourages" people to check
latest update and I don't think in any possible way has a downside
except for a little more text to email which I assume it's OK.