I received this rooted Kimo about late May, I guess. As I said, it's doing well with leafing out but I still worry about the soft, wrinkly look.

Has anyone else experienced this with Kimo?

Kimo is notoriously "Skinny"
I have a 6 foot tree and they grow tall and skinny!
When you cut them to prepare for rooting they tend to shrivel up like a raisin.
I have 4 cuttings potted up right now from June 16th and mine are all leafed out nicely but still have raisin skin!
Now... this is my opinion once they develop a good root system and this fills out the cutting to a more normal appearance.
You say you purchased yours with roots, don't be shy about watering your Kimo, as mine sat out in 3 days of Florida rain and are starting to fill out better!
Make sure sunlight and or heat warms the growing container it's planted in and keep an eye on it.
Don't worry and if you get the chance post some photos.
Aloha, Stuart