Comment 1 for bug 692587

ad PATH: This is by design, therefore it won't change. For example, by pulling in PATH from pam_env, the ability to specify different paths for different crontabs would be lost.

I'm speaking as one of the Debian maintainers here - Ubuntu is of course free to add a patch on top of our version. I'd advise against it, not only for the reason above, but also because most (could be all, haven't checked recently) versions of cron I'm aware of do it this way.

ad crontab(5): the manpage you linked to comes from bcron, not vixie-cron. However, using the manpage search thingy, I couldn't find the correct one either...