Route Policy in Dynamic VPN Tunnel

Do you have only one dialup IPsec phase1-interface on the HUB side and terminating all IPSecs from other FGTs? You probably need to separate the phase1-interface for each peer to set policy routes.

But BGP generally doesn't work well with policy routes because it always decides the best path for one destination prefix unless you use tricks described below:

https://www.noction.com/blog/equal-cost-multipath-ecmp

To make policy routes to work you need to have multiple parallel routes in your routing table ("priority" can be different), like two 0/0 routes pointing to two ISPs and a policy route specify one of them.