From empirical evidence in my Legacy, I think the +10 Presence requirement is only finishing the conversation chain for each Companion, not maxed out Affection. Finishing the convo chain generally takes less than 10K Affection to do.
This is correct.
And if anyone is interested, about 1/3 down the page are the "companion affection triggers":
You can see how many affection points it requires to trigger the final conversation for each companion (so long are you are in chapter 3 of your class story).