Whatever you want to call it, mixing unlike recyclables together is bad news.
When single stream (also called mixed, or co-mingled) recycling was first implemented, it involved mixing glass, plastic, metals, and paper all together in a single compartment truck. Eventually the glass industry protested, and glass was removed from many curbside programs. Thank goodness some communities had sense enough to find other ways to collect glass, separate from other recyclables.
Many people think their curbside recycling program, (whether they call it single stream, co-mingled, or mixed recycling), is working just fine because the single compartment truck contains only paper, plastic, and metals.
It’s not fine, and my bet is your community does not have a recycling transparency ordinance. And I doubt you can see the trucks dump in real time. The most important player in your recycling program is the end-user, the company trying to make a new product from the stuff you left at the curb. They did not ask for unlike items to be tossed together.
Why don’t they speak up? Because they have been backed into a corner by an industry that has way too much control over our recyclable assets.