Been keeping an eye on my LGW - SVQ (Seville) in mid June, and a quick look on Expertflyer this morning and it has been zeroed out in all classes for a date I am looking at. And for many other dates I randomly picked in June.
However if I go onto BA.com and try book tickets for the same day, they are still for sale.

Is the zeroed out thing a precursor to cancellation, but they still allow tickets to be purchased? Am I reading that right? Or is it an Expertflyer issue/anomaly? Thanks.