If you are using tutor-ecommerce plugin on top of tutor, then the plugin might be the source of your configuration (of course if you didn’t check it)
Otherwise it might be hardcoded in payment MFE and that would be very strange.
I asked the question again in #ecommerce in Slack.
@pshiu was gracious enough to answer me. Thanks Phil.
Correct. As of time of writing, this appears to be the way the <PaypalButton> is coded in frontend-app-payment: https://github.com/openedx/frontend-app-payment/blob/master/src/payment/checkout/Checkout.jsx#L226-L231