Let me clarify a few things. First I'm not saying there is anything better or worse about split grade printing. And I very often use multiple filters in a single print, though not the max hard/soft split technique.
Second, the high and low exposures do not have to be equal for the result to be the same as using an intermediate filter. The only requirement is that there be no separate burning and dodging adjustments during the hard and soft exposures. You could have a grade 0 exposure of 8 seconds and a grade 5 exposure of 3 seconds. There is an intermediate filter that will do this in one exposure (+/- maybe a 1/4 to 1/8 grade). And I wouldn't trust anyone who tells me they modulate contrast in 1/8 grade increments.
Split-grade is just a different way of doing things.