Think Skyeurope Salzburg flights simply not released yet.
Winter timetable sees Bratislavia inbound arrive at MAN at 12.20 and outbound leave at 19.00 on Weds and Sats. Cant see aircraft being parked up all that time.
Thomsonfly launching 'frequent' Salzburg flights this winter so maybe they are seeing how they perform before commiting themselves. Rotation could always be used for another destination.