Yes there might be a good correlation between dogfooding in senior management and great products, but it's not worth shoving a square peg into a round hole to meet this superficial criteria.

The reason Facebook and Twitter executives use their respective services is because that is the core product from the very beginning. Google+ on the other hand is a tertiary product. Just because management realizes they need a foothold in social doesn't mean that they should forcibly try to transmute themselves into the target market. Instead they should have people in charge of the product that care enough to use it naturally, and I think that's what they're doing.