It's not really a strange move, Labour were essentially forced into giving teachers the 5.5% as that was the independent pay review body recommendation, which does not apply to FE. They 100% did not want to give teachers a 5.5% pay rise but it was sprung on them by the last government who deliberately didn't reveal the pay review body recommendation when they were given it, well before the election.
The problem Labour faced was a recommendation that was higher than expected, when one of their main pledges was to recruit 6500 more teachers. They couldn't reject the recommendation that was made in response to a recruitment crisis by pleading lack of money.
The pay review body recommendation doesn't apply to FE. Labour AFAIK didn't make any major pledges related to FE teachers. Government departments have just been told to make £billions in cuts.
So politically, it's perfectly understandable.
Obviously that doesn't make it any less shit for FE.