Thanks for clarification. Maybe this is more accurate: Taproot enabled a CiSA soft fork by adding Schnorr. CiSA was not also included in Taproot because there is still a lot to discuss including which MuSig to use.
MuSig isn't detectable, so we didn't need to decide "which" to use. It was more about making sure we can preserve backwards compatibility correctly and handling sighash flags weirdness
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