If I understand your question correctly, you want to know if a Check Point appliance mimics Fortinet behavior when Stateful Inspection (Allow Asymmetric Routing in FortiLanguage) is disabled? Just to be clear, Fortigate behavior in this scenario is:
- No UTM Policy applied
- Firewall acts as a router and just forwards packets (no firewall policy lookup)
In my experience the Check Point does not act in this way - firewall policy lookups are still done and things like IPS, AppF, URLF etc. all still work, i.e. it is not disabled just because you disabled stateful inspection. My answer is not based on any official CP documentation, but on experience with a site I inherited a while back where Stateful Inspection was disabled for some reason.
Do note that a lot of traffic will break if you disable SI, think of stateful return traffic initiated through an outbound rule that will now be dropped - also because the various threat prevention engines might not see the whole connection there will be a negative effect on the ability of the gateway to inspect the traffic.
Again, this is based on my experience and I stand to be corrected. I will verify this in my lab later latest tomorrow and report back.