Watching swimmers training

It's always interesting to watch people train and go through their drills; lots of which are familiar to me from my days as masters club swimmer, however some of the drills do puzzle me a bit - it seems like they are just something else to do.
Watching one particular swimmer was interesting as she alternated between 'catchup' and her normal stroke.  I quite like the catchup drill when it is purely used as a patient leading arm reminder, (just so long as we don't touch hands in the front of the head, which can lead to encouraging the arms to cross over). Anyhow when she was swimming catchup she was dropping 4 strokes in the 33m pool and was faster than her normal swim stroke (I timed her). But after each catchup lap, she reverted to her leading arm pulling back almost as soon as it reached full extension.  So why did she not take on board anything from her catchup sets and lengthen her stroke for more speed?  It's mystifying.

If we are not integrating elements from drills and focal points into our stroke to improve technically, then there's no point in doing them.