I stayed out of the discussion about the CSUSA Apprentice Jr. Gent because I haven't examined the kit, but I agree with you that it does look like the Rizheng Jr. Gent. I bought a few hundred of the Rizheng kit when they were new and they did have a problem, the centerband was too large for the tube. Rizheng corrected the problem by supplying replacement centerbands that had been turned down to a smaller diameter. Actually they were then too small, but at least they could be glued into the tube.
Since then Rizheng went out of stock on the kit, then back in stock when they received a new shipment, and they introduced a fountain pen version of the kit. I recently got in an order from the new stock including the fountain pens. The centerbands on this new order have been turned down to a smaller diameter, they were not cast smaller, the lathe marks are still on the inserted part of the bands, just as they were on the corrected centerbands that they sent in response to complaints about the original order.
The problem with the Rizheng Jr Gent was never with the bushings not fitting properly. I bought 50 sets of bushings, I tested them myself and sold most of them, no problems or complaints. The problem found with the CSUSA version related to the bushings not fitting. My guess is that they did not purchase their bushings from Rizheng, they had them made somewhere else and the size was not right.
To the best of my knowledge, Rizheng does not make the Jr. Gent kits or bushings, they buy them from another source, same as CSUSA does. Chances are that they are both going to yet another source(s) for bushings.