I hear this all the time, but I've never seen an Op Spec that required it. Do you have a copy of one? A restriction on an operating certificate, as mentioned by another poster, is a different matter. NetJets has one. Do any others?

As far as POIs go, they are NOT the definitive authority on aviation regulations. Some may think they are and many take their word as gospel. But they are frequently wrong. The legal opinions linked here are what really matter.

I personally know the circumstances surrounding the Nichols letter from 2009. That company was erroneously telling pilots both verbally and in the GOM that pilots could log SIC time, because the company required it. There was no Op Spec or certificate limitation. Lots of 135 operators do the same. It's probably just another carrot dangling ploy to get low time pilots to work for them.