I have seen the video, and the only thing I see is a bodyguard doing his job... Leonor is the future Head of State of Spain, and in a territory where they know there may be hostile radicals, they must take all measures.
When there is a crowd of people spontaneously gathering in the street, they cannot check one by one, so they must react quickly to any gesture that they may consider excessive or dangerous. When the Royal Family approach and mix with large groups of people is a moment of tension where they must be very alert because at any moment there may be an incident, from something dangerous to a push that causes falls. Leonor and Sofía are young, have little experience and probably still have to develop reflexes to mark the limits more in front of people.