There are two different kinds of sounds. On flat hit, you hear a higher pitched wood sound.
If you really get the topsheet to stretch and rebound, while compressing the sponge you get this corking sound which is lower pitched. That sound is actually from the speed of the rubber rebounding. Like when you take a towel or a whip and whip it and it makes no sound and then you do it just so and you get a big pop....that is what happens to the rubber/sponge when your contact is a very particular kind. The speed of the rebound, the speed of the topsheet snapping back to its original position creates that sound.
That can happen without good boost or speed glue. But nowhere near as easily. It is much easier to get that with a rubber that has been boosted well. And even easier to get that corking sound when you use speed glue.
But, without the technique to really get the ball to sink into the topsheet and distort it, compress the sponge and really stretch the topsheet while the topsheet is grabbing the ball, you won't get that pop (corking sound) that I am talking about. So, technique + chemicals are quite useful to the process. Said differently, whether you like it or not, the-don has a point.

Maybe the boost isn't the whole picture. But he does have a point.