I thought HH was Sheikh Mohammed bin Zayed? Whatever, it's certainly not Sheikh Mansour and the emails said HH would "arrange" the extra funding. That funding comes from Abu Dhabi, probably the Executive Council, not ADUG so it's not owner investment.
What I assume has happened is that all the due monies were sent to ADUG for onward transmission to City and that Soriano's request to Pearce to have these split out is precisely because they need to ensure we avoid accusations of equity funds being mixed up with partnership revenue. Which is exactly what I'd expect from an organisation trying to ensure everything was whiter than white.