With the classic app you can definitely have one lock mirror another lock, with the understanding that there may be a few seconds delay because the first one has to send a message to the hub which then has to send a message to the second one. That part is easy.
The problem is there are almost no Smart devices to replace the regular handle, regardless of brand, because the mechanics get really complicated. Much more complicated than a deadbolt.
So just go out and do some research and see what you can find that would replace the handle set, and then you’ll see what I mean. An electric strike is usually the best option.
Sorry I can’t give you more details today, I’m just really tired and this would be a long explanation.
But the synchronization part is the easy part. Finding two devices that would fit on one door at the same time is the hard part. Especially if you don’t want it to look like a Hannibal Lecter enclosure.
But if you’re OK with that look, then sure, with the classic app you can have the bottom one unlock automatically when someone unlocks the top one.
(The Schlage lever without a keypad that was posted upthread is not a smart device. It’s just a manual add on handle that matches the smart deadbolt stylistically.)
You might be able to use an August for the top piece, which then would look better on the outside, but it will still look institutional on the inside.