It’s in public preview. The docs dont’ look very ready now. This is what they state:
Payment on invoice is a popular way for customers to buy now and pay later in Germany. When you accept payments on invoice with Stripe, as soon as a payment is approved we add the full payment amount, minus fees, to your Stripe balance. We then send an invoice reflecting your branding to the customer. They must pay the invoice within 14 days.
So basically, Stripe is trying to catch up with buy now pay later options.