What I have understood is that the threshold of 900 is the limit where you switch from LCG to HCG. The only advantage is to get back to a full dynamic when switching from first mode to second one. It seems that for cameras like Zwo or QHY this is transparent for user because they switch automatically between the two modes.
After the choice of LCG or HCG is up to the user. Maybe for lucky imaging or use of filters like L-Extreme from Optolong HCG might be better than LCG.