"It's them, they're impossible"
Some evenings you'd defend yourself. It isn't that you have a temper. It's that they're impossible at six o'clock. They whine, they ignore, they fight each other, they can't do the simplest thing. Anyone would shout.
Two things are true here, and the book needs both.
The first is that the child's part is real. Wang and Kenny found a child effect. Children who behaved worse got shouted at more the following year. Children aren't blank, and some are harder than others, and the six o'clock version of most children is the hardest version of them. The NHS page on difficult behaviour puts the reasons plainly. Often it's because they're tired, hungry, overexcited, frustrated or bored. At ten past six an eight-year-old has been up for twelve hours, hasn't eaten since lunch, has just been pulled off a screen, and is being asked to do a chore. Every one of those conditions makes a child less able to comply, and you've got all of them at once.
The second is that the same conditions apply to you. You're tired and hungry and at the end of a day too. So ten past six has two people in it, both depleted, one of whom is holding a pan of pasta. That isn't a child being impossible. It's an hour in which nobody is at their best, meeting a ladder that turns not-at-their-best into a shout.
There's a thing to notice about what "impossible" expects. An eight-year-old is eight. A five-year-old is five. They aren't small adults who've decided to be difficult. They have the attention, the self-control and the sense of time that their age allows, and the tablet is more interesting than the table to anyone, at any age. Some of the fury at six o'clock is fury at a child for being the age they are. I don't say that to scold. I say it because it's a mismatch you can fix in your own head, this evening, and it takes the personal insult out of "In a minute."
So the answer to "they're impossible" isn't "no they're not". It's that six o'clock can be made less impossible, for both of you, by changing the conditions rather than the volume. A snack at half past four. Screens off by a timer and not by a parent. Tea a bit earlier. You eating something too. Chapter 19 lists these. They're dull, and they remove more shouting than any amount of resolve.