Could it be that James Cridland (npub13cg…ck4q) it's using https://podcastindex-org.github.io/docs-api/#get-/search/byperson and that's a different endpoint? (the old one that uses the PI web search parsing the description) [1]
And not the new :
api.podcastindex.org/api/1.0/episodes/byperson?q=alberto+betella&max=5
PD: Just guessing
[1] https://podcastindex.org/search?q=alberto%2Bbetella&type=person