Question on eBird alerts and the birds not showing up

As a birder coming up on one year of taking it seriously, the eBird daily digest of needs birds and rare birds is appointment reading for me, and I love both the site and the emails. But I had a question, let me lay it out in bullets:

*I get the needs emails for all of North Carolina, not Durham County (which may be the issue I'm having)

*The other day, I was browsing the top birders in Durham, and saw a checklist from a guy with maybe 10-12 birds I didn't have

*These birds did not show up on the daily eBird email despite being logged there in my home county a few days earlier.

What's the story there? Is the email alert only picking and choosing some, but not all? Can people opt out of having their logged finds appear in the email?

For those curious, this was the list I was browsing- - and there were several birds there I don't have that never made it onto my needs alert email.