I note in the headforpoints communication today they say...

"When should you book an Avios flight as a return?

So, you may well ask, what is the point of booking Avios flights as returns, given that I have less flexibility? Here are a few reasons:
Because you’re using a BA Amex 2-4-1 voucher so you don’t have any choice – one voucher cannot be used to book 2 x one-way flights on separate tickets"

This is not my understanding when using online booking to capture availability without contacting BA by phone and subsequently putting the two separate bookings together releasing avios for the 2nd passenger for the second booking per the wiki?