Single-use credit card numbers are an alias for your credit card number, allowing you to give each online merchant with whom you do business a different number.
The other point that has been covered in every review is the fact that, if you only have one single stream CableCARD (The Series3 support two single stream or one Multi-stream card) then you can only use one tuner, even on OTA, despite the fact that there is no technical reason for this.
The single solution on a card joins tap-to-pair functionality and ease-of-use of NFC with speed, coverage and performance benefits of 5G WiFi to create the ideal platform for highly-mobile devices.