Yes because 1st is better for gaming.
And it's proccesor is good enough for video editing.
If you only rate PCs by the fact how well they do in gaming then you know very little about PCs. Gaming is just one task of many what PCs can do.
Reason why i don't suggest i5-9400F build is because that PC isn't balanced. And by balanced i mean CPU performance relative to GPU performance. i5-9400F is slightly below average CPU while RTX 2070 is above average GPU. i5-9400F can keep up with RTX 2070 but barely.
Most of the times, as time goes onward, people will upgrade the GPU to keep the PC up with the time. Upgrading CPU is the hardest thing to do and it's also very tedious, so, the CPU usually remains the same until completely new PC is bought/built. Due to that reason, if OP would go for i5-9400F build and upgrade the GPU in the future (e.g GTX 1080 Ti/ RTX 2080), i5-9400F would be too weak to keep up with better GPU and bottlenecks will rise.
i5-9600K build with RTX 2060 is far more balanced since i5-9600K is above average CPU and RTX 2060 is average GPU as well. Upgrading GPU in the future to e.g GTX 1080 Ti/ RTX 2080 will not produce any bottlenecks due to the better CPU performance. i5-9600K is even powerful enough to run RTX 2080 Ti bottleneck free. Even if there is slight bottleneck with RTX 2080 Ti, i5-9600K can be overclocked (from 3.7 Ghz to e.g 4.7 Ghz) which removes any bottlenecking issue.
Due to the fact that most people buy their PCs for several years to come and GPU is the main component that get's upgraded, you also need to think ahead when suggesting PC build to go for. Sure, at the current moment, the i5-9400F build is better at gaming (which is just one task) but in long-term perspective, i5-9600K build offers better performance (future proofing).