Autoinvest issue?

Quick question,

Why can you set the auto invest value less than what is allowed as a minimum deposit into a pie?

I can only deposit £50 minimum into my pies but I can set my auto deposit to less than this. Does this mean that my auto deposits will then just go to the “cash” section until it reaches the minimum £50 deposit into the pie itself?

Would it not make more sense for this feature to be set at £50 rather than allowing deposits to sit idle?