You either arrest someone in order to interview them if they're a suspect (which he is) as it is part of the interviewing process, or you ask him to attend on a voluntary basis.
I would assume because of his age, he was arrested, taken through to the custody block and immediately bailed to return for an interview at a later date as there is not much necessity to take away his liberty, but there is a need to process him formality and impose the restriction of him probably being banned from football events (as part of his bail) and to return to the station on the agreed date.
Or they could have interviewed him there and then if they had the capacity to do so.
Why would they need to search his home? He hasn't been arrested for an offence in which there is outstanding items and seizing his phone would not prove anything other than his search history including Bradley. However this can be proven without the need to seize a phone as there is video and photographic proof already