Yep. It's not generally a HUGE issue in these engines, there's a long drawn out procedure in the shop manual for bleeding the cooling system but I don't think I've ever needed to use it, they're usually pretty easy to bleed.
If worse came to worse if you backed the cap off a hair and drove it around, that would get the air out of the system pretty quick.
Typically the space you're seeing in the degas bottle after you've ran it and it's dropped after you've had the system open is the space that the air was taking up somewhere in the system is now being taken up with antifreeze, causing the level in the bottle to drop.
The worst trouble I've had bleeding any engine is if the system is TOTALLY empty, block water jackets and everything. It can be avoided by pouring coolant into the bottle slowly, as this allows the air to come out of the degas bottle opening as it fills from the bottom.
I like the RADKITPLUS vacuum cooling system filler, but apparently it's not endorsed on the 6.4 anymore, since Ford seems to think the vacuum causes the seals to come off the thermostats. I've used it on hundreds of trucks, and never had an issue.
Part of being able to do a 6.4 rad swap in a little under 40 minutes, from start to finish