Side banded external rotation exercise

[Triatus]

So for the banded external rotation (arm by side), I usually never feel it and keep my arm tightly adducted to my side. If anything I’ll get some irritation or feeling in the front of my shoulder. However today I decided to try these again and just left about an inch between my elbow and side, I didn’t get any anterior discomfort and actually felt my infraspinatus working. Everywhere seems to say keep your arms tight by your sides but doing them as I described above seems to work for me. Is there any reason I can’t do them like that from now on? (Or any suggestions as to something I’m doing wrong when completely adducting to cause anterior shoulder discomfort)