I understand how it looks but one thing I learned over the years when someone is leaving is that it is in fact best to let them leave now rather than hang around. Even good people, including friends are just not the same when they know they are moving on. Even co-workers get sick of it after an amazingly short period of time.
Working out "notice" just does not work out so well no matter how much good faith there is or how professional someone is.
In fact, in some cases it is really horrible.
As a result, I don't really think badly of an organization when it has no interest in letting an ex employee hang on for any time period.