If it's American Style Tango beginning bronze, it's probably supposed to be Promenade w/ Right Turn to Back Tango Close. If that's the case, the "collecting" of the foot you're talking about wouldn't be in lieu of the forward step on the RF, it would be in addition to it.
...and if you think about it, it has to be that way, because if the following step was with the LF as you described it, then you would have actually changed weight on to your right foot in place, which is not just a mere "collection", but an actual bona fide step. So either you forgot about, or at least forgot to mention the forward step on your RF following the "collection".
Now regarding the collection itself, keep the following in mind: In the end, it's supposed to be nothing more than a position you pass through on your way from "A" to "B", without stopping. If your teacher is having you stop, it's probably a training tool to help you learn the timing (and by "timing" I'm not referring to musical timing, but rather the relative speeds of your body parts to one another, your body as a whole to your partner's, your travel to your rotation, etc). Often during the learning process it's necessary to slow down or even stop to train your body into the right positions and to do things in the right order, at the right speed, etc. But that doesn't mean the ultimate goal is to stop.
Or at least, let's hope not in this case. There's a reason that the left-turning version of promenade is known as "Promenade with Left Swivel", whereas the right-turning version is merely "Promenade with Right Turn". In the Promenade Swivel, the lady turns in front of the man using a pronounced (and often stacatto) swiveling action, around a fixed axis of rotation -- in other words, the progression is temporarily halted and the turn is done in place. The Promenade Right Turn, in contrast, is not done with the man literally swiveling in place in front of the lady. It is a continuous progressive rotation between steps 2 and 3, or as the English might say, a "Pivoting Action".
For this reason you ultimately will not stop to brush or "collect" your RF. It will simply pass by the LF on its way from one position to another, perhaps slowly but nonetheless continuously. And if you think about it, it should do this more or less automatically, because that brush position is already on the path from A to B. Just as when you walk straight forwad, unless you swing your foot outward in some unusual manner, the feet should always pass narrowly by one another.
Watch that video clip of the Promenade Right Turn again, and notice that Melissa's RF does indeed brush past the LF, but without a pronounced stopping action. Then watch the video for the Promenade Left Swivel, and you'll see the brief stop as she turns in place on her LF. This is by design, not by accident.
Regards,
Jonathan
