UDP is UDP - no matter which port.
If there are too many UDP packets hitting a firewall interface, some will be dropped.
Default Packet Handling can't block this.
Here is what would happen, from the docs:
"For example, if you set the Drop UDP Flood Attack threshold to 1000, the device starts to drop UDP packets from an interface that receives more than 1000 UDP packets per second. The device does not drop other types of traffic or traffic received on other interfaces."
You could add a Custom packet filter for UDP 443, set to denied From: Any-trusted to Any-external, to prevent this traffic, and force TCP 443 to be used.
Also, you could disable QUIC in Chrome.
Disable QUIC in Chrome Browserhttps://help.clouduss.com/ws-knowledge-base/disable-quic-in-chrome-browser