EBU Single Rulebook Q&A 24 January 2019 2019_4484 Strong customer authentication requirement on pay-by-invoice payment transactions

Does Article 97(1)(b) PSD2 apply for pay-by-invoice when the payer's funds are covered by a credit line extended by a payment service provider? When a payer pays by credit card, the payer's funds which are transferred to the payee are covered by a credit line extended by the credit card issuer.