"Absence Calendar Direct Reports Current Month" - How does it work 'normally' (but with custom SQL)?

Summary:

I was editing the logical SQL of a seeded analysis and noticed that while it appears to have custom logical SQL, it still works just like a normal subject area analysis.

• Custom logical SQL would normally cause the Subject Areas in the analysis to display as "Invalid Subject Area", but this one doesn't, it behaves completely 'normally'.
  • This analysis has four select statements (joined with UNION ALL)), but there is no evidence of this on the "Criteria" user form.
• Moreover, when I copy and paste the SQL back into a "new analysis", it then reverts to normal behaviour (i.e. displays "invalid subject area")