The 12-pin power connector may have been removed from the RTX 3070 Founders Edition. The card remains out of stock in most countries, but NVIDIA has tweeted a marketing photo clearly showing the card with the conventional 8-pin connector.
https://www.notebookcheck.net/NVIDIA-may-have-already-killed-off-the-12-pin-power-connector-on-the-RTX-3070-Founders-Edition.506459.0.html