Really nice job, JFC.
I, too was gobsmacked by the perfect alignment until you revealed that the fillets were added after the doors. I'd never thought of doing it that way! I've always built a face frame in the work shop which is almost inevitably then forced slightly out of square when fitting. I'm going to try it your way next time!
I know you hate painting but wouldn't it be easier to at apply at least a couple of coats of primer before fitting? I'm lucky enough to have a spray booth so would completely finish the job prior to delivery. Your decorator has done an outstanding job all things considered.
It just goes to show that the much derided MDF has it's place in modern woodworking. For painted jobs like this it clearly outperforms solid wood.
Also, for all my love of working with fine hardwoods, I find that this sort of job in MDF is generally more profitable!
Once again, nice work
Brad