Compressors need to be compact because of rpm limits. So they have to use splitters to limit boundary layer growth.
The diffuser needs splitters because model size engines have too little room for single channel ducts.
This has been proven in professional applications where 10% more thrust and 5% less fuel burn was achieved.
The Wedge diffuser is OK but the 90 deg bend causes massive flow breakaway and as a result the air accelerates into the engine.
It can be so bad that removing the diffuser can have same result in performance.
So at the bend we need to accelerate the air so that we reduce the breakaway.
Its the lesser of 2 evils.
We accelerate air by reducing the height of the channel at the bend.
This is result of 10 years of work with Supercomputer and CFD.