"Suomynona. Her we go again straight from the book. Progressive Chasse to the right has the count of 12&3
that means that the 2nd and 3rd steps have half a beat only on each step."
Yes, the amounts of time are given in units of beats. But it doesn't say which fractions of a beat of duration match with which fractions of the measure.
If I tell you something has a duration of "1" I haven't told you if it takes place between 1 and 2, or between 1.1 and 2.1 or 1.5 and 2.5 - I've just told you how long it takes.
And we also have to remember that the given durations are between the official boundaries of the step, which are the instants of foot passing, not the instants of weight change as many would nievely assume. If you want to change weight on the beat, then the steps last from sometime before the beat (or musical subdivision) to sometime after it, not from beat to beat. As long as all the steps have the same given duration you can ignore this, but once you allocate different divisions - 12&3 or SQQ - you have to pay attention to exactly when you are counting from if you want to argue formalized timing.