What are the mechanics of private API beta badge/reputation rewards?

Question

Update:
George Edisons comments appear to explain most issues raised here (if not all), so I reformulated the question to reduce the noise and allow for an answer accordingly. I have considered to delete the question instead, but apparently it triggered one user to assess and resolve the lack of private API badge assignment to him, so there appear to be some useful outcome of my procrastinations at least ;)

Background:
I have been looking at this topic with the assumption that the private API beta worked just like the Stack Exchange 2.0 private betas, where all activities are at the target host starting from day one and only the access barrier is lowered over time. However, if I read things correctly now, the private API beta has been hosted on a separate site, which got migrated to Stack Apps later on with manual steps involved.

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After one issue of reputation inflation via multiple badge assignment has been resolved recently, I'm again confused by this topic due to the introduction of the latest procrastination playground - the new per-site reputation leagues do show for example:

• Sorting by August
  • yields 1 user being rewarded the API Beta badge despite being a member as of Aug 12 only
• Sorting by June
  • yields 3 users being rewarded the API Evangelist badge, where some don't have any posts before May 21 (start of public API beta) and some don't have any posts at all - see my related question What constitutes 'active participation' in the private API beta?
  • yields 5 users being rewarded the API Beta badge, where some are a member as of May 21 or even June only

Maybe the whole registration/membership has been reset after the private beta and the badges are triggered by the next visit only, but this doesn't explain the API Evangelist badges and could qualify as a confusing bug in the 'member for' display at least. Besides, looking at the API Evangelist badges in isolation yields users with posts after May 20 only and no posts or no activity at all even.

Is it possible to get this explained/sorted without dissecting any case individually?

Answer 1

Before StackApps, there was a small group of people privately testing the API. After some time, StackApps was created and everyone was notified so that they could move their content there.

A handful of people who had actively participated were hand-selected to receive badges. The badge was awarded as soon as the user registered on the site.