What a non sense. After you have finished your MPL with TR and basecheck you can move to any other airline. In the worst case you only have to change your TR... The Sterling guys were actually a good example: they were all hired by other 737 operators. On top of that this was in 2008 and the authorities have all become one under EASA since then so there is no way they can stop you from swapping airlines
So in short: go for it. There are not many good options out there and if you have the choice by a sponsored MPL with a job at the end or a speculative CPL with nothing at the end it is a no brainer!
