It is phisically impossible for the main sensor to get a closer focus compared to the smaller sensor of the note and s10. If you calculate the focals and minimum focus distance the one of the note and s10 is much shorter.
the mimum focus distance is not related to the lighting conditions at all.. as long as the sensor is able to see something it will be able to focus as it should.
It is debatable whether we can call the use the ultra wide lense to focus closely something comparable to the main sensor of the note 10. Personally I do not think it is meaningful and it may be fancy to patch the hardware fault of the s21 ultra main sensor when taking a casual picture of a flower but for what I have seen in a situation where you need a photo to be a close up and be usable without any silly distorsion like photos of book pages the ultra wide produces non usable results