Continuing the discussion about noinput / anyprevout

In a Bitcoin development discussion, the idea of creating a new opcode called OP_CHECKSIG_WITHOUT_INPUT was proposed as an alternative to SIGHASH_NOINPUT. However, one participant in the discussion pointed out that there wouldn't be any meaningful difference between creating a new opcode and making a new tapscript public key type. The only difference would be in the encoding of the code. The proposed new opcode would ignore any SIGHASH flags on a signature if present. It's worth noting that how sighash flags are treated can be redefined by new public key types.