This affects regenerated hearts (empty hearts get removed)
It seems they only update if somethings happens to your health (e. g. you take damage)

Adding something like this in ItemRingHealth.java fixes the problem

@Override
public void onUnequippedCurio(String identifier, LivingEntity livingEntity) {
    if (livingEntity.getHealth() > livingEntity.getMaxHealth()) {
        livingEntity.setHealth(livingEntity.getMaxHealth());
    }
}

(Referenced from https://github.com/ochotonida/artifacts/blob/1.19.x/src/main/java/artifacts/item/wearable/belt/CrystalHeartItem.java)

Thank you very much for pointing this out!