By general rule, anything where an eticket is issued, you hold a confirmed booking.

But there has been some recent changes.
The ECJ (European Court of Justice) was addressed with the case where an OTA send out a booking confirmation and the passengers party claims, if you receive that says booking confirmation, no matter if it comes directly from the airline or from the (O)TA, it means your booking is confirmed under EU261.
The airline argued, if its not a real eticket receipt coming from them directly or the travel agency fwding that document, the booking is not confirmed.

So the ECJ had to rule on this, not sure if thats in the papers yet, but the general consens was they'd agree with the passenger, which is a big too extreme.

Think about you only hold a reservation with a travel agent, they send you an email and say its confirmed, but its not ticketed yet, and the airline changes their schedule / cancels that flight, even thou you're not ticketed yet, EU261 would already apply.