"I can only feel a deacceleration at the end of the step if there is to be a turn."
If that it the case, then you aren't doing it right.
"Otherwise we are midway between the two feet at th extent of the stride just the same in the Foxtrot and Waltz."
No, not the same. The movement is along a different path, thus the midpoint of that path cannot be the same.
"Aren't you one of those who take the second step of the Natural Turn on the same line as the first step."
Yes, but the vertical component of hte movement will be different between various types of figures, even between various types of natural turns. Also the CBM will be different. There mere fact that the foot goes in the same direction for two steps does not in any way mean that the step is the same!
You have to learn to look beyond the tricial details, to the core of the matter. Or else you will never be a dancer, just a sophmore who likes to misquote books.