I reckon if Bitcoin has any physical property, it would be the energy used to operate and protect the network. Not the hardware that operates the mining or nodal networks, but the energy the runs the miners and nodes. Now, consider El Salvador with their volcanic geothermal energy, definitely observable and physical. Same goes for stranded natural gas burn offs, solar output stored in a battery, etc. Energy fuels the proof of work that is integral to Bitcoin. So really, it's not much of a stretch to say Bitcoin does at least have physical attributes. One thing I know for sure, Bitcoin can certainly be converted into just about anything one would need in the physical world.