I think as long as the purchaser is with you with their ID it's ok. If phases permit then ST holders/members can buy additional next week and obviously can't use the extra seat themselves. Ticket site states
Please note: As with previous years all ticket purchasers names will be written on the ticket and an ID check will be made at The Amex by stewards. Supporters must have their Season or Member Card/NFC season ticket registered on their phone or Photo ID.