The expansion chamber takes the two-stroke and makes it good at a certain RPM range. Before that, you were losing massive compression and massive fuel on every stroke, regardless of RPM. When the expansion chamber was introduced, you suddenly got a bunch of legendary power if you kept it on the pipe (think about that expression) and treated it properly. This guy is arguing that if we could come up with a system that didn't lose compression at ANY range of RPM, we could have legendary power all over the chart. Although this would be good for going fast around a track, I have to say I'd not like it myself because it's that "on the pipe" nature that bikes 2T's fun, so any "cure" would be a hard-core race solution.
Believe me, I know what difference an expando can make. When I first got my '67 Kawasaki 120, it really didn't have one. Then, we found a guy who wanted to restore his 120 to stock condition and was willing to trade his hand-made straight-pipe with expando and stinger for our stock pipe. We drove there, made the trade, and unleashed the Dogs of War. Even before the bike was started, you could feel and hear extra crisp "pop-pop-pop" that wasn't there before. Upon starting the bike, the old sound of a mild dual-sport machine was replaced with a radical snarl and crackle that echoed of any building or tree within a mile. Rather than exhaust coming out in little puffs and wafting upward, it was now shot in blue bullets a good six feet out the back of the bike. The power was like stepping from an 85 up to a 250. I think my particular expansion chamber is tuned for low-end, too, because that's where all the power is. It pulls like a V-8 in the low revs, and even thought it's only got a 115cc engine, you can lift the front end off the ground with ease in 1st or 2nd gear with no clutch or body movement involved. One time I was riding a trail and I decided at the crest of a long, rolling whoop to give it a crack of throttle and put the front end up a bit. It went up a bit. Like, so much the bike was nearly sideways when it came down again.
And regarding reed valves, the '81 Maico 490 didn't have them, and when riders put reeds on the bike, all they notice is a slower throttle response. I'll grant you that for an otherwise-pipey 125 or even 250, they can help a lot. Woe to the poor, miserable bastard to sucks one into the engine, as will inevitably happen, though. With piston-port, your intake is indestructible. Can't break a hole.