Everything I've read about the procedure on flat towing a Focus says that you should immediately turn the ignition off after seeing the "transmission ready" message.
edited to add: I just glanced at the owner's manual and there's nothing that says you should wait until a "put in park" message appears. My interpretation of the manual implies you should immediately turn the ignition off after seeing the "ready" message.
If you've misplaced your manual, I've attached a screenshot of the page giving the procedure (page 184). I've outlined in yellow the procedure if you have an ignition key --if you have a push button start, the procedure is similar and giving on the other side of the page. And if you need the full PDF version of the manual, you can go here:
2018 Ford Focus Owner's Manual
The only other thing that I remember reading about the Focus is that it is important to disconnect the battery to make sure transmission problems do not occur.
I've never owned a Focus, so again, I'm just going by what I remember others reporting. But let's see if any Focus owners respond to your inquiry.
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