I don't know. Years of being a Semogue tragic coupled with the realisation (after dumping 8 of them in the forlorn hope that all were factory outliers) that they're just crap sounds convincing to me. With that make of brush you're lucky if you happen to get one that works almost properly rather than you're unlucky to get one that doesn't.
Also what needs to said in evaluating brushes is the difference between face and bowl lathering. Far more than with a bowl you can evaluate the backbone and how a brush behaves as it's in almost constant contact with your face. It doesn't really matter with a bowl because all you're really using it for is to paint pre-prepared lather on your face after all the real work has been done.
I've rebuilt loads of brushes and on one or two occasions have made the mistake of setting the knot too high, which is in essence what Semogue are doing with their brushes, and there is nothing worse than trying to face lather with a brush that develops these chasms near the tips because there's just not the hair density at the working end of the brush to hold the lathered bristles together. Your 1305, although not as pronounced as
@pyrokov brush, does the same. Boars, as
@alfredus has rightly pointed out, will tend to do that for a bit anyhow but as I've said previously, deliberately constructing a boar brush to exhibit that kind of behaviour is daft if you ask me.