I think the whole point of a savings account is that it's not an investment. Thankfully.
Banks don't use deposits when lending out money. They create the loan amount out of thin air. There are regulations as to how much they can do that relative to their assets. Thankfully.
What the economists mean by "creating money" is that people treat deposits as cash, and therefore have the feeling they have cash when they have a positive balance on their bank account, where in reality all they have is an IOY from a bank. But their cash is not in the bank anymore.
This is a common misconception. The reality is that banks lend money at interest rates above what the central bank offers them, meaning they can lend as much as they want irrespective of deposits, and then borrow reserves from the central bank at a lower rate.
Banks don't use deposits when lending out money. They create the loan amount out of thin air. There are regulations as to how much they can do that relative to their assets. Thankfully.