I disagree. Other UNIX/UNIX-likes still use /var/www so it's not merely "historical". The FHS doesn't say that anything in /srv has to be a directory rather than a symlink. What it does say however is:
Distributions must take care not to remove locally placed files in these directories without administrator permission.
... and unfortunately that is what is happening here (though more accurately they're being moved rather than removed).
Actually, on reflection, rather than doing what I suggested above, I think the package should just leave the contents of /srv well alone and leave its management entirely in the hands of the sysadmin/user.