The current rule is ‘sick off run on holiday, pay straight time for actual time worked plus additional 8 hours for holiday - medical documentation required for all sick on holiday’.
We say since the co worker has made himself/herself available by working then became sick - we say the pay must be the whole run. In addition to that no medical documentation except for filing the employer sick form when returning to work.
This is not like a situation where the co worker is calling sick from home on holiday.