That observation is fascinating to me. Isn't it possible that we're judging it with adult eyes? To me, kids can filter out "ui complexity" that's not relevant to whatever exploration they are doing. Examples I think of:

A microwave oven[1] might have 25 separate buttons on it but a 6-year old will know the 2 buttons to press to heat up the popcorn. Yes, the keypad complexity handles more advanced techniques of 2-stage cooking with different power levels etc but the child just ignores all of that.

Or, how many of us grew up with those multi-component integrated stereo racks?[2] The front panel has all those buttons, sliders, knobs, and lights. And yet, a small child knows how to turn the FM knob to find his favorite radio station or rewind a cassette to replay a song.

I also see video games[3] that 6 to 8 year olds play (even if the game wasn't intended for that younger age group). To me, the screenshots show a complex "dashboard" at the bottom of weapons or other status. (I'm not a Starcraft player and it all just looks complicated and confusing to me.)

I think kids can look at the "complex" F12 screen the same way as microwave ovens, stereo receivers, and Starcraft screens: ignore the non-relevant UI elements and just type "alert ("hello");"

[1]https://www.google.com/search?q=microwave+oven+keypad&source...

[2]https://www.google.com/search?q=integrated+stereo+rack+turnt...

[3]https://www.google.com/search?q=starcraft+ii+screenshot&sour...