Another reason is that the time it takes for the Dutch oven to come to temperature depends on a lot of parameters (size of Dutch oven, size of oven, fan or not, power of oven) so pre-heating allows for the timings to be consistent.
But I agree on the safety concerns so I will try your method on my next loaf, now is not the time to get bad burn wounds.
My personal experience is that bread is sensitive enough to parameters that you’re going to have to “get to know” your equipment anyway end do some experimentation.
Yes, timings will definitely vary. I timed how long my oven took to preheat with a cold dutch oven, and it was around 20 minutes, so that’s about how long I add.
But I’ve found the timing is not super critical, the main thing is not to undercook. (Note that most recipes say things like “check for doneness, and bake for another 5 minutes if the loaf doesn’t sound hollow”.)
But I agree on the safety concerns so I will try your method on my next loaf, now is not the time to get bad burn wounds.