Hello jegrasso,
Thanks for asking the Apple Support Communities about charging your Mac. The article you came from only talks about Fast Charging.
Please check this article about charging: Charge your 14-inch or 16-inch MacBook Pro - Apple Support
"You can use any of the Thunderbolt 4 (USB-C) ports to charge your Mac with a USB-C charge cable. Your Mac charges over only one port at a time, so connecting multiple power adapters to the MagSafe 3 port and Thunderbolt 4 (USB-C) ports won't result in faster charging. If you connect more than one power source, your Mac charges only from the adapter providing the most power."
The specifications also point out that model can charge from any of the 3 ports, but only one at a time: MacBook Pro (16-inch, 2021) - Technical Specifications
- "Three Thunderbolt 4 (USB-C) ports with support for:
- Charging
- DisplayPort
- Thunderbolt 4 (up to 40Gb/s)
- USB 4 (up to 40Gb/s)"
Though it looks like you are correct, only MagSafe 3 cables work. "MagSafe 2 and MagSafe power adapters aren't compatible with MagSafe 3."
Thanks.