Well it's a bit hard to discuss the op (didnt watch video) without familiarity w/ fps genre or cs:go or cs:1.16
Because otherwise it's an issue with steam iff cs isnt played in offline mode at dreamhack (dunno how it really works) but i guess the concept can apply to all steam client games. Dunno if LoL has unique game client for their lcs system they have (riot games, the maker of league of legends, has set up an organized format in each region--notth america, europe namely--and have a whole system for qualifying to a world championship. That is organized much differently than other esports that rely on LAN tournaments like dreamhack or online teamleagues or collections of leagues rather than one, consistent league year-round)
I dont know warcraft3 but starcraft brood war, the greatest esport, of course had LAN support and offline play so no hacks could be used. But now major titles sometimes have special competitive clients w/ a local server set up at LANs so that the general game client isnt used
There is not really stopping anything online except hack detection and watchful eyes, just as how it is no different from something like online poker or chess using engines to analyze for you when playing online in their online formats where it might be banned