Depending on the company, you often have the option of either a group or a private cremation. Group cremation is what you described, but private cremation ensures you only get your pet’s ashes returned. The company my vet uses even offers the option for you to be present and view the cremation.
I’m curious why you assume almost all were willing participants. I’m also concerned with the use of the word “coerced”.
The promise of good money doesn’t ensure willingness, and just because workers are “street level” doesn’t mean they aren’t being exploited.