A pubkey could of course nonetheless use follow lists to signal not that the followed key is interesting, but that it is human and not a spammer. It's ultimately a matter of intent and convention. But yeah, using follow lists this way might be confusing, and have technical limitations. We currently have basically only two pre-defined modes of expressing approval or disapproval of a pubkey, through public following and public muting. Expanding this to include other information - e.g. "is human" or "is not a spammer" - seems useful, although one wonders how far the range of pre-sets should go (one could have verifiers for "is safe-for-work", "is appropriate for children" etc.).