Hi Pinky,
The matter being discussed was a delay at forming a lineout. The sanction for this is a free kick and no option to have a lineout. (19.8d) The non-offending side can opt for a scrum instead of the free kick.
21.4b relates to offences after the lineout has formed.
At least that is what I have always believed/been told. I will clarify the matter further and get back to you.