Sure, but non A-listers are boarding later so there won't be an extra person boarding early in the process.
I'm not sure what you mean. While they would be boarding later than A-Listers, if they bought EBCI, especially far in advance, they could still be "early" in the process.
To be clear, my point was that this isn't currently limited to just A-Listers, and that it might be problematic to do so.