That was more or less my take away as well, it forces you to deal with most of your technical debt up front and not let it pile up to some indefinite point in the future.
Essentially brutal purity is a really strong anti-kruft coating. Since kruft can't stick to your code, it tends to stay nice and shiny well into the future, unlike the dirty impure code elsewhere that builds up a nice thick layer of kruft over time and eventually collapses under that weight (or else some poor soul ends up spending a bunch of time either scrapping all the kruft off, or just throws it out and builds a new one).
Essentially brutal purity is a really strong anti-kruft coating. Since kruft can't stick to your code, it tends to stay nice and shiny well into the future, unlike the dirty impure code elsewhere that builds up a nice thick layer of kruft over time and eventually collapses under that weight (or else some poor soul ends up spending a bunch of time either scrapping all the kruft off, or just throws it out and builds a new one).