to clarify that is called an innerlink vs. someone with another site linking to you which is a backlink
do you mean like sitewide link?? IMO it is better to link from different sites rather than have a sitewide link...
There is benefit from getting more than one link from the same domain. It adds to your link popularity. If the link anchor text is optimized it will help you get up higher for that particular keyword. You can even have a link on every page of the other site and it won't hurt you.
I think he is correct, especially if you are using different anchor texts, it will make the links seem more natural to the search engine.