Interesting post, thank you.

maybe I am thick...

"The way it should work is funds clear to eBay first,"

If they clear to eBay they have to clear to somewhere....so where are they cleared to...an Ayden account ?

My quick google grabs have me finding this ...

wiki :

Ayden is a Dutch payment company that allows businesses to accept e-commerce, mobile, and point-of-sale payments. It is listed on the stock exchange Euronext.

Ayden offers merchants online services for accepting electronic payments by payment methods including credit cards, bank based payments such as debit cards, 
bank transfer, and real-time bank transfers based on online banking. Ayden's online payment platform connects to payment methods across the world.
Payment methods include international credit cards, local cash-based methods, such as Bolete in Brazil, Internet banking methods, such as IDEAL in the 
Netherlands and Mobile payment methods, such as blank in Poland. The technology platform acts as a payment gateway
payment service provider and offers risk management and local acquiring

eBay Australia benefits of managed payments :

1. Simpler to sell: Checkout is more flexible, with an easier experience for buyers. Buyers will have access to new ways to pay, including credit, debit and gift cards, Apple Pay, Google Pay, PayPal and After pay.
   
   Is this to say then that a platform such as PayPal , which eBay clearly disclose as being a beneficial means of payment for members, is going to also let a Dutch payment company get in the middle of payment and receipts of two PayPal account holders ?