The RTT tables are what you want.
Basically, “ping” is a traditional reflex when running into network problems. The introduction post for fly ping, its user-mode WireGuard implementation, motivated it with the example of verifying minimal connectivity to the gateway node. My own impression is that fly doctor, fly dig, fly ssh console, and fly pg connect have now mostly superseded it, as recommended diagnostics.
To my knowledge, fly ping was never intended for benchmarking…