I know I am opening a can of worms,but many top dancers will close the foot in the Waltz slightly ahead or back of the other to ensure the their dancing is progresive. If you don't believe me take a look at Gleaves teaching vidio where he demonstrates the basic waltz the same tape that he says to count the halve as well as the whole beats. In a lock step it's common to see people place the third step in a possition where they have to move back befor going forward, I think this why they now call it a cross step?.

Feet must close perfectly parallel on the rise, but should already be apart (but with knees still close) by the time the standing heel touches the floor.

Many advanced dancers use a minimum number of foot closure steps however.

Suomynona. Michael Barr very recently said. That it is nice to see the basic 1 2 3 being used instead of syncopated and passing steps with the timing of
1 & 2 & 3 & Very refreshing was said.

Part of the reason foot closure isn't seen so much at high levels is that it takes extreme expertise to round out the bottom of the downswing when lowering from foot closure. How often have you seen a couple start their waltz with a natural into some derivative of a spin turn, but the lady can't commence to rise as she passes over her forwards step 4 because the couple is either still lowering, having not rounded the bottom corner of the swing, or has fallen off the step and gotten their legs to wide, so she's stuck between her feet with no power.