Skytyping has never been banned in UK airspace as it has never been conducted here before. The activity is classed as basic formation aerobatics (not exceeding 30 degree angle of bank) and formation separation is anywhere between 40m - 80m dependent on altitude, so not exactly a risky undertaking for a fully qualified and experienced formation team. Skywriting meanwhile requires more abrupt manoeuvres to deliver, and so I am guessing that they are referring to an earlier ban of this activity due to safety concerns.