Comment by killerstorm

In almost all cases EVM smart contract interaction looks like a function call which can be easily decoded into JSON if you know ABI.

HW wallet doesn't need to understand the contract logic, it just needs ABI, which is generally a simpler task. Also it can show the name of function you're calling as selector is a hash of a name.

Safe is a bit more complex as it also wraps it in EIP-712 message, but that can also be decoded in a systematic way.