I was going to say “I’d be surprised if organ support is a large issue to an adult. We already have long term astronauts and people who are bed ridden for a long time during recovery. I would expect an issue during development though.”

Turns out there is research in this direction: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2379624/pdf/can...

It seems to say that there is a long term impact on connective tissue hardening… but it blames lack of stretching; not lack of downward force. Any regular movement would seem to fix that.

However, internally, organ tissue probably ‘bounces’ more due to gravity during movement… so less gravity means less flex of connective tissue.

TLDR: you seem to be right