It would be a lot nicer if you showed how it worked on the Mavic RC, but he can't since he doesn't have one.
I would not be so sure that this would work or not.
Each end of the phone slides in a certain distance into the holders. When your phone is fully inserted into the RC, this sunshade may or may now fir between the holders.
Just wait until companies start receiving them and they have fully created something as they have the actual Mavic RC to work with.

Also doesn't really allow for good access to the RC controls and screen from what I can see IMHO.

I own one of this company's shades for the tablet I use with the Phantom 4.  These shades are created with a 3-D printer and pretty expensive for what they do.  They are sturdy, but, the plastic is susceptible to bending due to heat from the sun and not very carefully finished inside the frame.  I would not want to put my nice iPhone or Android phone in one for mounting to the Mavic's remote.  Unless this model is better made than my tablet shade and finished out in a way that inspires confidence your phone isn't going to get scratched up, I would look for a different solution.