The printer will have been stopped, maybe, the line will not - a bit of poetic licence. When I was working on lamp manufacture, changing the brand was just a gravure plate change and took experience and a very few seconds to achieve. Anything that got through minus a stamp was just pulled out and put back into the line downstream of the printer.
I have no idea about these but most brands went with whoever had the best price for the right volume at the right time. It would be easy enough to tell from the metalwork inside who most likely made them (based on my experience with ECC types).