With that deep a footing and a gravel base, it sounds like in a cold climate. I would use one to stop the spring warming of the shed and contents from drawing the water vapor under the slab depositing on shed's contents to rust.
If any ads are present below my answer or words underlined/colored, I do not condone/support/use the product or services listed/linked to, they are there without my consent.
WELCOME to the forums, if I forgot to say it!
The Following User Says Thank You to Gary in WA For This Useful Post: