I remember something similar when I was younger. I don't remember the exact situation, but one day some other adult told me to do something and the reason given was "because I said so". When my mom learned this she told me "because I said so isn't a reason. If someone is asking you to do something, but they can't explain why, you don't have to do it.".
I like your variation. There isn't always time to explain in every situation and always explaining afterwards is a good way to develop trust that you do in fact have a reason.
I'll add another side-effect of always making sure you follow up with the promised explanation.
99% of the time, they don't really want to know "why?", they want to stall. Now they have to sit though an explanation. You can make it as short or long as you want. I.e., there is a cost to asking "why?". Not sure if that's the greatest lesson, ymmv.
I for one think salt and pepper hair is ridiculously attractive, Pierce Brosnan definitely had a big part to play in that. I look forward to rocking greying hair.
Sometimes I get angry when my son doesn't do something I ask him. In most cases the real reason is that I just don't want him to get hurt. Like I will ask him to not climb on something and he does it anyway and the third time I'll get angry.
Anyway one piece of advice is that it's really important to explain (and if necessary apologize). So I will explain I'm not really angry, I just really don't want him to fall and hit his head or something. After you explain yourself your kid will probably understand you better and listen more.
"Kill 'em with kindness." Worked pretty reliable for me.
Edit: Just saw that this is /dadvice. Sorry, I thought more in terms of general advice. For dadvice I'd say: "No path in vain", meaning always take for example a plate with you and put it in the dishwasher when you are on the way to the kitchen anyway.
After getting consistently sick when mine where toddlers the doctor suggested this and magically never again. Even when they were running the craziest stomach viruses:
Under no circumstances ever eat leftover food from your kids plate.
Why?
These guys go daily to a virus randomizer incubator (school, daycare, extra activities) and have all sort of asymptomatic things running through their systems.
Food gets mixed with saliva and turns into a culture of the randomized stuff.
I get uptight about little shit and then I feel horrible for making a fuss about it. There's only so much apologizing you can do before your kids second guess going to you. I've worked on it long and hard but it still comes out before I think first. As much as I try to not be like my parents it still comes out at times. Your advice is really spot on.
One to give out is to think about what needs to be done without asking your partner for a list or whatever. Be the good equal partner and that will help make you a better parent