I'm curious as to why you'd consider the "lack of open flame" be a disadvantage? I would have assumed in a closed environment where things could potentially catch fire, the lack of an open flame would be an "advantage". According to the specs, all of the fumes, smells, etc. are vented to the outside. Not sure how true that is??? I certainly don't want the cabin smelling of diesel all the time.
The simple explanation is that every professional chef would prefer an open flame for temperature control. It's not a small thing for people that cook. However, the type of cooking that benefits most from an open flame is best done outside the camper.
I would argue that an open flame is safer because the on/off is clear. Propane is less safe than diesel, but not unsafe in a proper system.
A diesel cooktop is the equivalent of a flat electric cooktop with poor temperature control. That's fine for many people, especially non-cooks, and cooks who will do most of there grilling outside anyways.
Some people would do better with no installed cooktop. Use potable open flame cooktop inside or outside as needed.
I'm not against diesel cooktops. I went with propane after listening to peoples evaluations. Many people are happy with them. Some people regret the decision due to the factors I mentioned.
Diesel is pretty much a "slam dunk" for heat if the extra cost isn't a deterrent. Less so for refrigeration and cooking IMO.
As far as smell the issue is some odor coming from the outside exhaust, not the inside. From my experience I could smell it if the air was still, but not odor was not strong. Since were using diesel powered vehicles there is probably some desensitization to diesel smells over time.
