Unfortunately so . . . You may not have to drain the entire 12.2 gallons but they're mounted just low enough (gravity-wise) to where it becomes ooze city if you try to spin them off without lowering the fluid level. I didn't have enough containers to experiment how much. When it got to one gallon, I stopped.
I guess it really doesn't matter. The filter change interval is the same as the fluid change interval now.
I am now officially terrified of the 400 hour service cost. This HST+ will clearly be MUCH more expensive to operate than my GST L39 was.