Shove some cash under a mattress or store it in a vault and you can be sure you are holding real dollars not fractional ones. Just holding a real dollar says no

Shove some cash under a mattress or store it in a vault and you can be sure you are holding real dollars not fractional ones. Just holding a real dollar says nothing about the value of the dollar you are holding. Same as just holding a real bitcoin says nothing about the value of the bitcoin you are holding. Outside forces affect the actual value of what you hold fractional or not. The ability to self-custody affords you nothing. The value in either case can plummet completely outside of your control.