That is a problem that we all have. There is so much material on the web, from supposedly authoritative sources on the subject of exposure which is just wrong. Then there is a large group of unknowing photographers that unwittingly absorb that information and as a result end up with a mental model of photography that simply doesn't work. Then there's another group of photographers that wrongly believe themselves to be knowledgable. propagate the errors and even go as far as to try to defend the errors from the people trying to help beginner photographers onto a path which will allow their understanding to grow.
That would be you.
Obviously the exposure is controlled by the luminous energy over the exposure time. In the case of a long exposure with a flash in the middle, the light from the flash adds to the exposure. The extent to which the shutter or the flash dominate the resulting exposure depends on the relative light power of them. It's not a problem with the definition of exposure, it's a problem with exposure not being as simple and obvious as trianglists would like to pretend (mainly because they don't have enough understanding to even grasp the basics, yet alone the more involved situations). And I should note there, unless anyone gets hot under the collar, I'm not referring to any individual there, only a hypothetical group of people that I call 'trianglists' who have unfortunately based their understanding of photography on the triangle and as a result understand very little.
But not in direct relation to the ISO setting. On a car the accelerator/throttle control controls the throttle. On a modern car it will also affect the ignition timing, the mixture and possibly also the valve timing and the induction tract length. It would not be useful to tell learner drivers that the accelerator was an ignition timing control to the exclusion of it major function.
Absolutely and completely incorrect. Now your turn to dooooo some homework Try reading up about mic sensitivity.
Sort out your knowledge of how microphones work before lecturing others to try to get them to adopt your faulty ideas of how sensors work.