By going direct to EE and not presenting as an existing BT Customer, you have bypassed the official migration route and as such BT would have the right to charge you an early termination fee when the line is taken over if you had time remaining in your existing contract.
The offers you were given through BT are reflective of whether you have time left to run on your contract at a specific price, as well as ensuring like-for-like service such as for those with BT Halo where many of these benefits have been carried over to the All Rounder or Full Works plans. These are more expensive than Essentials plans typically, but come with a range of benefits that customers may miss coming from Halo plans.
