Mexican Air

A question regarding air compressor exhausting on Mexican vs. American narrow gauge steamers. If I see it right, it appeared fairly standard practice for Mexican NG oil-burning steamers to have the air compressor steam exhaust line discharge external to the smokebox. The most common practice was to have this steam line terminate up behind the stack, and in some instances, above the cab roof. On a lot engines that ran up to the end of steam in Mexico, the compressor discharge line comes up to what appears to be some sort of shielded fitting. Now, I do not see this plumbing practice in use anywhere in the states for narrow gauge oil burners.
I suspect the reason for discharging directly to the atmosphere was to make the fireman’s life easier. He wouldn’t have to contend with a “jumpy” spot fire due to the periodic pulsing caused by the air compressor discharge messing with the firebox draft, threating all the while to put his fire out. This plumbing setup would be more advantageous for smallish engines on spot fire, switching and at stations. The loss of what ever draft contribution (had the line been plumbed into the smokebox) was considered an acceptable trade off to gain the more "steady state" draft arrangement.
Am I on track here,...or way off in the weeds? I would like some insight.