most other operators can do it like the thomson flight from leeds to tenerife thay bus crew from manchester which is less money but jet2 dont have a base in the south so thay would ether have to put crew up in hotels
So by your logic should I assume that all of the airlines that put crew up in HOTAC on a regular basis are losing/not making that much money? Also the routes you suggested are more likely you say, but they are completely out of character for Jet2!?
Either this is another one of those rumours like the NWI one (maintenance related hence PA-31 visiting), or there is something more solid in it. As I say, if there is any truth in this then the rumour posted by sxflyer is by far the most plausible.
As an aside, have Jet2 since closed their STN crew base?