Mine are out from hatchlings so long as the temps are OK and they have substrate suitable to bury into to thermoregulate. Obviously small torts have a smaller area outdoors than large ones to make them easier to find but they still need the same depth as adults as they do need the same overnight temps at certain depths.
My little ones are back inside now due to the danger of frosts but cold overnight temps are fine and it gets quite cold in my conservatory where they will be winding down for hibernation

Hope this helps.