I was talking about it with my teacher last week. I was encouraged to keep it planted.
I see people say that their teacher told them to plant it and I see the opposite. I don't mean this in a sarcastic way but seriously, "Who made them the expert." When it comes to classical instruments there is a body of tradition around how to play them. Sometimes people come along who innovate - or as others say break the rules or do it wrong.
The uke is a folk instrument and it has more than one tradition. I don't think there is a right or wrong way, just ways that work for certain sounds or styles and ways that don't work as well. I'm finding that anchoring my pinky is causing me muscle stress and is technically limiting. But as I'm playing I'm also noticing that sometimes it is useful and sometimes not so much.