Test of quality for benchmarks quality, versus, positive, accounts, indicate

Carson

LOS 47i, p 186 SS17 schweser

"Positive active positions - An active position is the diff between the weight of the sector or security in the managed portfolio versus the benchmark. For example...blah blah

For actively managed long only accounts, you would expect the manager to hold primarily positive active positions. If the manager continually underweights securities relative to the benchmark, this might indicate an inappropriate benchmark has been selected or constructed."

The professor's note below goes on to expand on this, but it makes it even more confusing to me.

This kind of seems like crap to me and I am looking for other opinions.

Just because the manager is long only he can't have negative opinions on the stocks in the appropriate benchmark? Even if we have created a sophisticated normal portfolio for th manager he would still have plenty of negative active weights wouldn't he? If he didn't you are basically saying the long only manager can't provide value by avoiding overvalued stocks.

Doesn't seem right to me.