Yes, it means that the plastic is going to start entering the good chain there. Plastiglomerate rocks mean that there are bits of plastic in the soil, and this will be consumed by plants and worms, which will be consumed by animals that eat them.

We are already quite touched by microplastics, checks show them everywhere in humans and their foods. https://www.nationalgeographic.com/environment/article/micro...

note that toxic things tend to accumulate more higher in the chain (animals) than lower (plants/trees)

this is not a good thing, if current plastics get eaten it will lead to more waste

Probably nothing we've built should belong in nature but probably we are part of nature too.