Back when HBD was very unstable, it made sense to use 100% HP if HBD was below the peg because the 50% HBD you'd receive would be undervalued. Conversely when HBD was overvalued, you'd want to stick with 50/50 to take advantage of the overvalued HBD (even if you immediately trade it for HIVE and power up, you'd end up with more HP).