Athens is due to pop (and settle) a second great prophet on t76. Definitely higher priority than Fredburg IMO.Besides the much higher failure chance (>30%), another problem with a double steal is that we would have to tech PH (for CoL) and run the EP slider some more before we can tech Currency. Stealing only CoL on t78 should work out much better. We would finish Currency just in time for the CoL steal.
We could have 4.5 HAs and 1 axe or chariot landing near Thebes on t75. That's probably still too early. There is no guarantee that the settler will leave the city immediately and not wait until Thebes finishes another defender, is there? Are we willing to delay the Fredburg attack for earlier Thebes and Athens?
I'm still happy with the single steal.
Edit: IIRC the settler can leave with a single escort, but we need to wait 2 turns before it's escort is out of range.