I agree that no amount of NO~X~ exposure is completely safe, but per the EPA and the WHO, some amount of exposure is safe enough. Otherwise, there's no point to specifying exposure limits. Per the link you provided, the WHO guidelines for NO~2~ exposure are 10ug/m3 (5.316ppb) for one year and 25ug/m3 (13.291ppb) for 24 hours. The EPA standard is 100 ppb for one hour and 53 ppb for one 1 year. None of the tests in the Dobbin paper showed concentrations greater than either of the EPA limits. The best performing fan that was tested kept concentrations under the WHO yearly limit, which was not exceeded for more than about 45 minutes with either of the other fans. That is in spite of the fans not meeting the CFMs claimed by the manufacturer.

Indeed, people might not properly install or use their exhaust fans, and there should be regulations and enforcement to improve on that, but that's just the way it is. Regarless of stove type, you need an exhaust fan for protection from particulates anyway. So if you have a gas connection, you might as well get a gas fired stove since it provides a superior cooking experience at a lower price point with fewer electronics.