A:Answer Anne,
I don’t know why the person that answered your question previously told you that the case does not work for the 3rd Gen iPad Pro 12.9”. The short of it is that the 3rd, 4th, and 5th Gen iPad Pro all have the same form factor and smart connectors. I bought this case for my 3rd Gen iPad Pro and it works just fine. As soon as I put my iPad in the case, the Logitech message telling me to download an app. I did that and everything else just worked. There are no gaps and the case fits snugly around my iPad, despite the newest iPad being .5mm thicker.
I added photos to this so you can see that I do have a third Gen iPad Pro. I also took a picture moving the cursor so you can see it on my screen and the typing test. This is a great keyboard and if you are in the market, I’d recommend it.
Logitech May have intended for this to work with just the 5th Gen iPad Pro, but it does work retroactively with the 3rd and 4th Gen versions.
I hope this helps you and provides an actual answer to your question. Good luck!