Not intended for partial furling??? I do it all the time and works like a charm to maintain balance and easier tacking.
"Not intended" means just that: it may work, but don't complain to Hobie if/when something breaks.
Generally roller reefing rigs have the following that plain roller furling doesn't:
-foam luff padding: there's a ton of tension on the luff of a sail (from the sheet, etc). When a sail is used partially furled, this tension is trying to tighten the wraps of the sail around the forestay, and the foam luff provides some cushion to prevent the wraps from getting so tight as to do damage.
-headstay foil: at least on larger boats, the roller reefing setups have rigid extrusions that have a groove for a bolt rope on them. this rigid extrusion keeps the top of the sail furled the same amount as the bottom, even when the sheet is trying to unfurl it.
-beefier furlers: all that tension on the sail is trying to unfurl the sail, and has to be counterbalanced by the furler. this puts a lot more load on the whole furler setup than when the sail is completely in or completely out.