rhm

It is really hard to judge the condition of old leather. I have an old Gretch archtop guitar, a lower end model from the 30’s, that I've had since 1982. It came to me with a thin leather strap that may have been original to the guitar. It's like 3/4” wide, not one if those phat straps that came into fashion in the 70’s. This strap was old when i got it and... well, almost 40 years later, I'm still using that strap with that guitar, and it seems fine. Apparently leather holds up damned well if stored in the right conditions.
As to OP's saddle, I agree that it doesn't need much, but what do i know. I am doubtful whether anything will actually soften it, but carry on, and let us know what happens!