I am reading specifications of BIP-118 that introduces the new signing mode SIGHASH_ANYPREVOUT. In the bip specifications, it is written that the addresses have length 33-bytes or 1-bytes length. In both cases, the public key starts with 0x01. If it has 33-bytes length, then we remove the 0x01 prefix and use the remaining 32 bytes, presumably as a taproot public key.
What I can't understand is actually how we use the 1-byte public key. In the BIP's specifications, it is said that, in this case, "use the 32-byte taproot internal key, p, as defined in BIP 341". What does it mean? Is this byte transformed to a public key with some key tweak as in taproot? I think that I am missing some logic around. I am a bit new to bitcoin and, usually, BIP proposals are written to be read by people that are already very familiar.