Since I have sold the Mini 2 with the old controller that needed to be attached to the phone and bought a Mini 3 Pro with the Dji RC controller that has the Fly App and screen all in one unit, I asked Dji Support if there was any need for me to keep the Dji Fly app on my phone, knowing I am not going to connect it to any controller anymore and their reply was a recommendation to keep it, and below is a screen shot as to their reason for it…
Did you know this?
It can also be checked on the remote if you connect it to Wi Fi.
Not really sure why they’re telling you that unless they think you still have the old drone.
I did tell them I sold the old one, so I was surprised too cause indeed the manual says that once connected to wifi or even to your phone as a hotspot, you can have access to all the feautres of the Dji Fly app.
go figure…
The App is a connection to your DJI account
There is no reason to delete it from your phone as it’s useful to check your flight data etc plus many other things like DJI maps or support or as a backup device if your RC controller wasn’t working for any reason
Also useful for quick transfer to download from drone to phone if you wish to share while out and about. I use it a fair bit
I see but how so, if I don’t have the old controller anymore how can I connect the phone to the Dji RC? Bluetooth-wise?
It connects the drone and the phone and then you can download the images. There are online tutorials on how to set it up. I have the RC which I fly with but use quick transfer with the Fly App when I don’t have a computer with me to download the images to the phone and then upload to Kuula for example.
Here is a good summary of how it works
Thanks for the amazing replies, cheers!! 
