http://linkagedesign.blogspot.co.uk
This is the place to have a look for a progressive curve. You can change the language to English.
The transitions are only a little progressive. I owned one and thought that whilst the coil shock was lovely around corners and over off camber roots it was not progressive enough overall and I swapped between coil and air regularly to get some pop back.
The Starling Swoop is a great bike, I owned one and liked it. It is most definitely not progressive and you really don’t get much from it with a coil shock. It feels super plush as it’s so linear but it’s hard work to ride and needs a lot of encouragement to leave the ground. That’s no slight on it, it’s a great bike with an air shock full of spacers fitted, it just a linear ratio.
I’ve not ridden an Airdrop Edit but the curve of the linkage looks more progressive than a transition.