Does a small amount of cannabis really affect driving? All the usa states that legalised weed should now have roads like mad max but they dont - you usually see a small increase in accidents at first then after the idiots have calmed down it settles back down to the same levels as prohibition states. Tens of millions of people with weed in them and roads as safe as ever - makes you think doesnt it?
Cannabis is used by a lot of athletes and jiu-jitsu fighters because it improves their reaction time and coordination - look up the “high rollers” jiu jitsu tournaments - quite a way from your idea of cannabis users and cannabis effects?
Maybe they were lying to you about cannabis eh?