Any code points, other references on using compression and set screw fittings on same EMT run?
NEC 110.2 you have to use [UL] approved equipment.
NEC 110.3(B) you must use equipment according to its labeling and instructions.
Any EMT couplings from competent suppliers comply with 110.2, and using them for their (one) obvious purpose satisfies 110.3(B).
Both are listed for the task, it's no worse than using different brands.