Sounds like what you want is "Split connections" in the P1 options.
IKEv1 is always split -- each P2 gets its own separate configuration
IKEv2 can combine traffic selectors and does so by default, so all your P2 configurations get lumped into a single configuration entry. This is more efficient and flexible, since it only needs to maintain one child SA for all traffic, but some other devices/services don't like it for various reasons.
If you are using IKEv2 and check "Split Connections" then it creates a separate configuration for each P2 so they will be independent.