Maybe it´s still of some interest for you - I did some tests with ISO charts and the result is as assumed. 4K/50&60p uses lineskipping/pixelbinning as FHD/120p does, so the vertical resolution is about half the expected in UHD/60p. I think it´s a little better than half the resolution since we have a oversamplingsensor here giving even good results in blue an red resolution as in blue/red situations that surpass native resolving bayer sensors.
Please consider that the UHD test charts were filmed in only half the size, so the FHD files have the standard 5,62% of the picture height, UHD has 2,81% of the picture hight per single chart (to be honest the charts were filmed nearly 2% to small). Charts represent 100% pixelsize coming out of the cameras. Tests were done in the center of the image, so corner performance will degrade due to lens performance and lens distortion correction.
I also did a test against the old Phantom 3 Pro and my Sony Alpha 6500. Charts are a bit different since I wanted to check resolution in lower contrast scenes. Result is that at least without motion there is no difference.
Since I live in a PAL country all these tests were done using PAL frequencies. I also checked NTSC frequencies and these look the very same as the PAL ones. So 30p looks like 25p, 60p and 48p looks like 50p.
For me this new drone performs very well, even against a 2.4 times oversampling Sony a6500. The old P3 Pro is easily surpassed.
What annoys me more is that detail quality ceases if the copter/image is in motion in real scenes. Picture seems to become somewhat "unsharp". Maybe this is caused by some ghosting the camera produces in motion, but I´m not sure yet.