Every time a fielder attempts to throw or catch a ball, there is a chance that an error will occur. Errors happen ... they are part of the game. There are guidelines about who to charge errors to in certain situations, just like there are around charging earned runs to pitchers, giving batters credit for hits, etc. A coach can certainly choose to keep whatever record they want of what happens in a game, and who does what how. But if there is going to be comparability with other players from other teams, then ideally you have as many people following the same guidelines as closely as possible, otherwise you lose credibility and stats become meaningless outside the immediate team. Personally, as a coach, I am going to know that the reason the catcher had some errors was because my SS failed to cover ... I don't need the stats to validate that. I'd rather have stats that are consistently applied.