Trip protections like delayed flights and lost luggage are not something I considered when using points reward bookings. So if you use UR points to completely pay for the flight, you're not protected with the Sapphire Reserve trip protection perks? If not, the optimal method if you want credit card protection is to use UR points but charge $1 dollar for the flight?
In their T&C they say this:
What is a Common Carrier Covered Trip?:
It’s also travel on a Common Carrier when free flights have been awarded from frequent flier or Rewards programs, provided that all of the miles or Rewards points were accumulated from a Rewards program sponsored by Chase Bank USA, N.A. and/or its affiliates.
Haven't done that specifically (I have filed claims when paying only taxes and fees on award flights) but that reads to me like you're still fine.