Just to share my experience....

I had been able to get my wife and daughter when they travel without me (not just separate PNR, I fly 7-10 days later) row 18AB on 777 (AC 15) for the last 6 years. I do understand the rule does say only if it is on the same PNR. This is even when I was the old AC*Elite for the first 5 years.

This year, I am SE and my wife is travelling alone this year and I still managed to get her 18B. I did get some agents (AC*E days) that bring out the rule, and I just do the "hang up and try again" until I get a agent that will do it for me.

On the return flight, same date different PNR, never have an issue.

I do explain the miles are from my account, blah blah blah... and (a big) maybe the most important thing I did say is the PAX is wife. And My wife never changed her lastname, so the agent really just take my word for it... unless they go thru the whole profile check with address, etc...

So, if you want, you can try telling them the other PAX is your spouse and see if that trick work.

Goodluck