110.12 because it’s ugly
110.2 Approval, Doubt my AHJ would approve it.
110.3(B) doubt the manufacture would approve it
230.7 if the elbow is for a Service
314.28 wire bending space, conductors #4 and larger, although that would be hard being the OP had a 1/2” in 3” as an example.
You have also introduced a threaded entry/lock ring/bushing in the elbow that is going to interfere with the other pulling dimensions/abrasion. Also depends on where this extra EMT connector is installed.
Is the elbow PVC with the EMT addition, now add a bond bushing in there.
I’m sure there are other articles that could be cited depending on the full details. But damn, it is hard to cite something solid on it. Thanks for putting me on the spot