The size of the drone is not some secret... you can search for the Mini 4 Pro on YouTube and find a bunch of hands-on reviews.
The DJI Mini drones are very compact. The DJI Air 3 is arguably the next level up in the lineup, and it weighs 3x as much and is noticeably larger. The "teeny-tiny drone" you're describing just doesn't sound comparable or particularly useful.
from experience I know that the SDK and battery life are better on the mid-range DIY options/
Aftermarket remotes/radios are arguably better; just not as compact and conveniently set-up.
I can't comment on camera/gimbal.
There are DIY-ish units out there that are entirely controllable via your choice of language; i'm not sure if there is any SDK that rivals that flexibility.
all that said : I understand the DJI value proposition, but the company has practices that I try to avoid entirely in my life, regardless of how nice their drones are.
The DJI Mini drones are very compact. The DJI Air 3 is arguably the next level up in the lineup, and it weighs 3x as much and is noticeably larger. The "teeny-tiny drone" you're describing just doesn't sound comparable or particularly useful.