These are the key points in the story:
* Working members - which includes neither Andrew nor Harry - of the royal family will wear uniform when present at five ceremonial events during this period of mourning the Queen.
* as a non-working member of the royal family, the Duke of York will not wear uniform, sources said, except as a special mark of respect for the Queen at the final vigil in Westminster Hall.
* neither Harry nor William are attending the vigil in Westminster Hall, which is only for the Queen's children - Charles, Andrew, Anne and Edward.
So if you want to read it that "they" found an event that Andrew could wear his uniform at and Harry couldn't attend, specifically so that Andrew could wear a uniform at one (out of five) events and Harry couldn't wear one at any events, then you could read it that way. Or you could read it another way! Personally, I think it's nothing to do with favouritism. Attending the vigil is hardly the main event.