My understanding of Oda still being with Katou after he lost his powers is cause hes hyper fixated on him. He believes Katou chose him to be special like him and like he said Katou is his 'saviour'. Katou does say he lost his powers gradually which could mean Oda didn't hear his thoughts for years and continued to be obsessed with him. So even when he started hearing his thoughts Oda kept his fixation, he even says he only truly likes Katou and judging from his backstory he had intense apathy before he met Katou so its highly possible Katou is the first thing hes truly 'loved' or wanted.
so did katou lost his powers, and oda on the other hand didn’t and started to hear katou’s thoughts just like the others (based on the extra) but oda didn’t leave him because??? man i would actually like to have this story longer or a volume 2 please ...