No. Sym 1 tricks gain more SR than they lose due to blizzard dumb ranking system - with enough hours, they'll gain 30 per win and only 15 per loss. The opposite effect of playing a regular character (soldier, genji, reinhart, etc.- where you'll gain 20-25 for a win and lose 20-50 for a loss) because so few people play it, it compares your 10 min overall game play per round to other syms (people who may only play once or twice a season depending on map) of the same rank (gold, plat, diamond, etc). Less competition on a character especially a niche character like Sombra, Bastion, Torb, Sym and at one point Mercy allows people to rank up to GM despite a losing record or even playing badly. They just have to out play the average person on the characters with enough hours put in.
Its why so many "mercy 1 tricks" (mains) are in GM now because no one played Mercy for most of Season 3 and Season 4 til they fixed SR gains for healers, but because of the low amount of competition on Mercy, people just massed 30-50 hours on Mercy only, and even with a 35-40% win rate you could rank up despite playing the character horribly because the amount of data to compare you to others was so low, the game ranking system thinks you are doing well.
If you actually watch the video you linked, that sym is actually get shyt on majority of the time, but despite being a liability to his team, he can still rank up because Blizzard ranking system is the worst in FPS history.
Basically the system rewards you for playing a niche hero despite losing efforts. It takes more than a few games for this though, takes hours, but if you got the patience and can stomach playing 1 character for so long - Play bastion, sym or sombra right now for the next 40 hours of game play and you will gain 300-500+ SR from where you are at right now even if you have a 40% win rate
