That looks like a pretty clever idea. It might work. When I was grumpy about the scritch from my best badger I tried brushing the tips across sandpaper (I know, sounds like a horrible idea), but it didn't do anything
This is a process that Semogue (and some other boar manufacturers but not all) uses in their manufacturing process, albeit with a lathe and iron rubbing bit rather than by hand.
Please look at time sequence 0:43 in the link below (takes you to a video) in which this process in being performed at Semogue. The end seen does not cut, but uses friction to induce and accelerate a process called flagging.
Boar brushes are pronounced in how they flag. To have a flagged tip is one that has split into thinner shafts to make the tips softer. Natural painting brushes (boar) have a process similar to this applied for well over 150 years that allows the brush tips to hold more paint and to paint in a smoother fashion. Here is a video showing the same process for paintbrushes.
Now not all boar hairs are the same in how quickly they flag. I have noted through experience in handling many different boar knots from different manufacturers that some knots require more flagging effort than others. Some users going the "all natural approach" of letting each shave and drying sequence to do this work on certain boar brushes have noted as long as a year before the brush is broken in enough. Others state that the same brush straight out of the box is totally satisfactory. That is personal preference which is subjective. Flagging however can be easily seen visually so the the level of flagging is a measurable by sizing of the end of the brush, not due to personal preference (subjective measurement).
What this individual (in the OPs posting) is doing is continuing a process that the end user rarely sees or thinks about when buying and using certain brushes. It will not harm the brush. The process just continues the flagging process. Eventually however, the tips are fully flagged which means that the hair ends cannot separate further and the brush will stay at this flag level throughout its life cycle.
Now you know the secret as to why Semogue brushes are desired by many users over other brushes.
P.S. I discovered this while doing a large amount of research into synthetics and integrated some of the information into my article series last year.
You can get the same results rubbing the brush on a smooth wooden board (like a cutting board) for a few minutes after each shave while the brush is wet if you have an new brush to accelerate the process or let time do the work but that is up to the individual user.
Actually, I've found Semogue to have by far the least split tips on arrival (Omega's are often well started splitting), but their hairs are more regular, generally thicker, more consistent in height (more % tops as Semogue calls it), the knots better shaped; etc: vs other boar brushes.