You are 100% on the money. The PCO private cash offers is the one that varies. Why some dealers are able to lock them in and some won't is beyond me.Guys - here's the TRUTH, super important!
Rebates and Incentives can only be applied and are good on the day you actually get/pay for your vehicle - transaction day. If there's a discount from Ford going on TODAY, there's no guarantee that discount will be going on (valid) at the time your get your ordered truck in (physical purchase day) - and if the dealer says otherwise, he's WRONG.
This was explained to me when I ordered back in October when I walked in and offered $1000 below invoice plus incentives. It was an unknown price because they have to get invoice first, and nobody knows what the incentives will be at time of purchase. It was explained to me very clearly how Ford incentives work.
Then when I got a call yesterday and was told while my build week is Jan 25th, it would likely take a full month for the truck to arrive (San Antonio, TX) - HOWEVER, the dealer told me that it was probably good news because I'd be creeping into far better incentives by that time (from Ford). Remember, the dealer and I already made our deal (1000 below invoice), so his profit at this point is 'fixed', so he's rooting on me to get better incentives because I'm battling cancer, that happened right after I ordered.
Now, keep in mind that by "Ford Incentives", I'm talking about the big and main ones from Ford itself, not anything specials your dealer may be running using their own profit margins. Also, this doesn't include those rare birds that got Ford offers in email/popups that have an expired time on them like coupons.
What I think is happening on the PCOs might be a bit of, sly of hand that other dealers may not want to do, Is all I can come up with. I have been able to do it with my dealer one other time back in 2016 on a 2015 model that was also pretty late.