I think I’ve figured it out. When IPv6 is enabled, there seems to be a system-level issue, and even the ISP comparison section on EA’s internet connection quality page fails to load.
I suspect it might be related to how the game is optimized for IPv6. I disabled IPv6 while keeping IPv4 enabled, and surprisingly, my connection quality started showing 99/100 consistently.
I played around 20 matches throughout the night, and I didn’t experience any lag, freezing, or muddy gameplay whatsoever.
If your internet connection is already good, I’d definitely recommend checking this setting.