A good way to solve the latter and understand why the former is not true (or if it is true, it's true of just about all European carriers), is to read the Ultimate BA Guide Sticky on the front page. Under seating, it will explain the concept of convertible seats which are very common intra-Europe.

The first few rows of Y are blocked to allow them to move the curtain without moving Y pax who have already reserved seats. The curtain will (in theory) be fixed at least 3 days before departure and those blocked seats will become free for Y pax to pre-reserve.