these videos should be shown to all umpires before a game. what is EHB doing about these - most of these tackles five years on are still blowing against the defender! More education is needed around this! I will start showing this to umpires after the game!
It depends on experience, even at higher level games, the umpires have the game time and knowledge to look for stick blocks. This may be a slow motion clip but briefing videos and umpire training sessions often use real games at normal speed to show how it's done. It's about reading the game and watching the tackles and interpreting the steps taken for the challenge. It may be hard to spot but those that can spot it are the ones who progress.