Sphere testing isn't for Q/A, the process isn't conducive to mass testing of product stocks. It's meant for testing individual light engine designs. There are faster and cheaper ways to detect out-of-spec or counterfeit inventory. I think HLG's problem was the all-too-common one (in China) of the fabricator-turned-direct retailer, given the plethora of QB knock-offs flooding the market. That and a not-exactly-unique design.
As for the PCB, it's half the product and where all the ingenuity, innovation and fabrication quality differences between LED strip/board products are found. Samsung supplies the diodes and controls their quality and design. The rest is the province of the board/strip producer, and it lives in the PCB. So in many ways, the PCB is everything. The diodes are generic. And yeah, skimping on the copper, or the trace widths, or ally backing, using old pick-and-place machines, etc., all makes a difference in the quality of the final product.
So I get their goal. I just don't know if the solution is to take fabrication in-house. There are plenty of quality fabricators with state-of-the-art equipment and practices in China. You just have to get off Alibaba and find them, and develop a relationship.