If you have ANY confirming information about this, send an email to hacks@blizzard.com. Be sure to specify who, what, and where they are doing this. Blizzard has made it very clear to be doing account boosting is against both the In-Game Code of Conduct and is against the rules in all Blizzard sanctioned Overwatch Esports Events (Collegiate, Contenders, and World Cup) with penalties up to and including disqualification from competition.
Blizzard also made it clear that throwing games, account buy/selling, and account boosting, are NOT permitted. They have dedicated teams that work to identify account boosting. (Source) However, as long as you alone control any accounts you have started AND you try to play your best, you are permitted to have multiple accounts. (Source)