A couple of thoughts ...
1) I'm not familiar with the encapsulation process, but with all of these examples of foreign material getting in the slab, is there any possibility of something similar getting into the inner holder (that actually holds the comic)?
2) So, with all of these examples of 'bad' slabs getting thru, one could assume two things. First, QC techs at CGC are very cavalier about their job. Second, if said cavalierness is a fact, do the QC techs sometimes see this stuff and just shrug and let it go out.