Not true.
Navigate on Autopilot is ALSO available even if the 2017 car has no FSD paid but with Enhanced Autopilot paid ONLY.
It's easy to confirm whether your 2017 car has Enhanced Autopilot by going to the car's screen and click on "Autopilot" menu.
If it has Navigate on Autopilot, then you would have a minimum of Enhanced Autopilot.
There's currently no way of knowing whether you have 2017 FSD or not unless there's a payment proof such as a Monroney window sticker, or some other kinds of receipts.
Since it is over-the-air software, it can be there in your car one day and mistakenly taken away the next day so you need proof that the feature was squarely paid just in case.