It's for performance in 2019/20 (pre-Covid, some of it maybe even pre-Avanti) and 2020/21 (Covid/emergency period etc).
Nothing to see here.
And yet, following the largely very successful financial year of 2019-2020, which ended only a couple of weeks after the first lockdown, most of their employees were asked to accept a 0% pay rise in April 2020, because of Covid...? They are not alone, of course, in that, but some resentment was bound to surface sooner or later, and may also be partly the cause of the current poor relations and the ensuing cancellations and timetable reshuffle.