Where did you see that claim? I see a different claim on their website:

""" How will the reserve be invested? Users of Libra do not receive a return from the reserve. The reserve will be invested in low-risk assets that will yield interest over time. The revenue from this interest will first go to support the operating expenses of the association — to fund investments in the growth and development of the ecosystem, grants to nonprofit and multilateral organizations, engineering research, etc. Once that is covered, part of the remaining returns will go to pay dividends to early investors in the Libra Investment Token for their initial contributions. Because the assets in the reserve are low risk and low yield, returns for early investors will only materialize if the network is successful and the reserve grows substantially in size. """

https://libra.org/en-US/about-currency-reserve/#the_reserve

Libra maintains "100% reserves." How is that money reserved? For a bank, it needs to be either in cash in the vault or on deposit with the Federal Reserve. Either way it's not getting loaned out again. Presumably Libra will be depositing it at (loaning out to) a bank, or putting it in short term bonds, money market, etc. Either way, they're loaning out all of the money, i.e. they have a 0% reserve.

What Facebook is proposing is merely to have assets equal to the deposited funds. For a bank, that is called teetering on the edge of insolvency. If a bank's assets ever dip below its liabilities, it is insolvent and either has to raise equity capital or be wound down by the government. This is why banks have capital requirements, so that they have a buffer against loans going bad.

> investing the deposits is not how they plan to make money off of this.

A huge float invested very conservatively still makes a lot of money. That is how most insurance companies actually profit.