Ping from source interface

I have 2 ISPs so I have 2 default routes , one with metric 10 the other with metric 20. Is this right? When I ping to the internet from the firewall with the “ping source” command the routing table will not be consulted, instead the ping is using strictly the defined source interface?

But when I ping the interface ip of the metric 20 ISP route from external,the return traffic goes via the metric 10 default route ( using the routing table)!? No automatic symmetric return path.

Thanks in advance