Interesting point on some caps being too big for the application.
But in this case I think the Mundorf Supreme SGO are in a similar size range to those being used - just better quality.
On the Muzishare X7 model I suspect the Muzishare silver label on the coupling caps is covering a Mundorf EVO silver cap. They refer to the cap as Germany in origin and has the same 1200VDC rating. I may have to try to peel the silver label off to see what is underneath. Maybe someone on here knows which caps Muzishare is rebranding?
The Muzishare X9 and X10 are using Mundorf labeled caps - EVO Supreme Oil.