you ever snowski?
how'd you learn to stop?
didn't you learn to snowplow with the skis tucked in towards each other?
Let's consider an extreme..
What happens when you mount the tabs VERTICAL and put them "down"?
You snowplow, right?
So if you go from vertical (fully snowplowing)
to horizontal (no snowplowing), then you can see that the more you stray from horizontal, the more snowplow effect you will have when you tab below neutral.
When tabs are mounted at a matching angle to the deadrise, and you run them neutral, then there is no snowplow, there is just additional "hull length". This is useful. But when you have to run them below neutral, you start snowplowing.
There are arguments both ways. I guess the real answer depends on how much tab you need to run at racing speeds.