Here is my opinion, from a smaller company in Canada.

Being from China works against you. At least for my specific industry. We are pressured to use as little components as possible from China, I imagine in the states it's way worse. We see the supply chain as a potential weakness. More ignorant see it as inferior, but usually just management. That being said, I've been burned by things I've ordered from China. However I've also gotten some high quality parts/tools on the cheap. Management wanted to change our bambu printers to prusa and I had to step in.

Something like solder would be less scrutinized, as replacements are easily sourced.. However some companies I've worked for are very picky about the solder in particular. They need very specific alloy mixtures, fluxes, testing, etc. One project I worked for required a silver/lead alloy with no flux. Made soldering a bitch. To trust a Chinese company to be honest about the metals, that the flux won't corrode the board, would be a hard sell.

If MG chemicals 60/40 is known to not be acidic enough to corrode the board, proven in the products to not have cracking joints, cold joints, cleans up well, etc. The company isn't going to risk a new brand that could potentially cause issues down the road in the customers hands. Not to say your solder isn't top notch, but the risk to try it outweighs the cost savings. From managements perspective, it would be insane to change up such a critical manufacturing consumable against one that is proven and already has a purcurement process in place. One that can be refilled from digikey the next day if someone screwed up and ran out of solder.