PieFed isn't hiding mods - when Lemmy fails to get them, it's for its own mysterious reasons.
In ActivityPub, to get the moderators of this community you can do this from the command-line:
curl --header 'accept: application/activity+json' --location https://feddit.uk/c/fedimemes/moderators | jq .orderedItems
To get the moderators of a PieFed community, it's exactly the same:
curl --header 'accept: application/activity+json' --location https://piefed.social/c/50501/moderators | jq .orderedItems
In both cases, the mods URL comes from the attributedTo
field for the community.