You are probably the only GG 300 2018/2019 owner who has fitted the right hand seat bolt. Originally the bike comes with one bolt only. No need to install a second one. And I have crashed my Gasser's harder than in your video
The swing arm covers you have are for 2018 and that is why they do not fit. I know 24mx sells them as "for GasGas 2018/2019" but they sell a lot of sh*t, like clutch springs and other parts that simply don't fit. On the 2019 the brake line holder is improved and has been moved further forward. Compare your pic with Gez's and you will see what I mean
Regards from Austria
Doc