Right?! This shocked and annoyed me too. Three male grandchildren walk behind the coffin, zero female grandchildren.
Not because they are the oldest three - Zara is older than both William and Harry. Not because they are higher up the line of succession - Beatrice and Eugenie are higher up than Peter. Not because they can't walk that far (Zara was an Olympic athlete, for God's sake. I'm pretty sure she could stagger across the grounds of Windsor Castle.) It's because Peter is a man, and someone decided it would look "right" for a phalanx of men to follow the casket. And I guess they thought Princess Anne might as well be one - she has spent her lifetime being the exception to the rules on gender roles.
I do not believe for a second Peter was there because William and Harry did not want to walk together. Neither of them is as self-absorbed or immature as that.
I doubt William and Harry wanted to follow the casket anyway, after the scarring experience of following their mother's. They should have had the non-royal family members arrive first, then the spouses children and grandchildren of every gender, along with the underage grandchildren. Then the Queen. Then the casket procession with the children and adult grandchildren in age order walking behind.
And as a single-adult household the Queen can form a support bubble with another household. So Camilla and Charles could have sat with her instead of leaving her all alone there. Or Edward and his family.
Also disliked the Land Rover hearse. (You had a special car made for your funeral? To drive you 200 meters instead of letting soldiers carry you? He "designed it" himself? You mean he said "Chop the roof off the back and load me on the bed of my old Land Rover when I die"?)
And the way commentators were so focused on whether Harry and William were or were not speaking was so gossipy and disrespectful of the occasion.