I don't belong to any LS forums so I assuming that wasn't to me...
A 30° seat will help low lift flow. But, at the expense of lift past .200. Jeeps, AMCs, and tractors use a 30° seat because they all use very small camshafts (lift wise) and the engines were never expected to make horsepower. Just low rpm torque. If the port design is good enough to support it, and one has the ability to use a larger camshaft, low lift flow is not what you want. Aside from the flow impact above low lift, it also makes reversion a much bigger issue because it flows equally well in either direction. So cylinder filling is compromised at low rpm too. Good porters do not want big low lift flow.
Just an FYI - my mentor still raced NHRA Stock Eliminator. He's in SS now but he raced for years in Stock Eliminator and had more than a couple ntional records. Enough that his SS car was given to him by Ford. He had about 15 years developing his valve job and a 30° seat had no part of it even though the camshafts were lift-limited to under .400 at the valve.