I get where you're coming from, and yes, even If no contract was signed it seemingly still existed given the verbal agreement which evidently existed (especially given somewhere states Sammy accepted the press release). However if Southampton came in with an offer even after this agreement, and...
Would you not do the same?
If I were offered a job, and then a (what any neutral would see as) better offer came along for more money, I'd certainly take it.
Just a shame it's us on the receiving end.