Exhaust Brakes and EGT?

[LRDG]

This may well be a stupid question Given that they have been around for some time and that with the Jacobs e-brake being MOPAR and Cummins approved, it very likely is, but the question still nags.

The exhaust brake works by restricting exhaust flow and creating backpressure in the engine. The question is whether there are circumstances when doing so will result in such an increase in exhuast gas temperature as to present problems and potential turbo damage? Better exhaust flow contributes to diminished EGTs, all other things being equal. So logic suggests that impeded exhaust flows should contribute to increased EGTs, all other things being equal. Is there some mechanism in the Jacobs e-brake set up that I don't get that deals with the "all other things being equal"?

I can understand that in open road conditions the flow interruption is such that it is unlikely to have any significant impact. But when the e-brake comes into its own is in conditions that suggest there should be a problem. Towing in mountainous/hilly conditions. This puts a lot of stress on the engine, many people may be running boxes that further increase EGTs, and the e-brake is regularly working quite possibly taking EGTs above a safe level. So the final question is what's wrong with this picture - what's missing that explains why that would not be the case?

I must be wrong, but I'd like to know why....