The bearings on mine are caged, but they simply rest inside the cup built-in to the hub. K7 hubs are supposed to be top quality, but there are knock-offs, since this is Chinese manufacture.
I'll give the guy you linked to an email, MagicValleyHPV and see what he says. The hubs he has look like they were made for pressed in bearings and are much stronger. The biggest problem with this eBike is the lack of rear shocks and a very heavy back end. I had one of the batteries in a basket in the front for better weight distribution, but the basket kept breaking and the extra weight over the front wheel made it handle strangely.
As it is now, it still handles more like a motorcycle than a bicycle simply because of the weight of the batteries. I could buy lithium batteries for it, but I consider that the cost (5 times what I paid for SLA's) to be vulgar.
I still park my van on Friday and tool around on the weekend on the bicycle. I just have to mind the weather this time of year. We've had lots of rain the past week in south Florida and it looks like that's going to continue.