If you encounter a scenario where your leg straps need to be "load rated" - in other words, let's say hold 10x your weight, You're probably not going to make it to tell us about it on the other side. If you're climbing properly and safely, and hunting properly and safely, there is no scenario where the leg straps on any saddle should be required to handle an impulse force much higher than double your body weight. Even that is a stretch.
The leg straps on the kestrel are not "load rated" for your protection - it's for New Tribe's. They are basically acknowledging that some person will use the equipment improperly, and hurt/kill themselves, and said person and their family will take advantage of US legal system to gain compensation from said misuse. In order to get complete insurance that covers against all of this, you make it impossible for the saddle to be even a tiny percentage of why a person is hurt.
That said - I do think have leg straps to help keep your saddle in place in the event of a fall or slip, will probably make things more comfortable for you, if not a wee bit 'safer'. To accomplish that, they need not be load rated. by the time the force gets that high on them, your saddle should be taking over and handling the fall. If it isn't, you're doing some weird stuff...