It probably depends on what you count as "understanding" and what kind of "complexity" you're dealing with.
Like if you have the sequence 14563241653246216435 then trying to write a program to recreate that sequence is probably more complex to do and describe than realizing that's essentially rolling a dice for 20 times. Not only is it more complex, it might even lead you down the wrong path of assuming that the concrete sequence matters in the first place and that predicting the next number is possible and not just a matter of probability.
Though it might be possible that the more complex model also gets you to the realization that you're dealing with a homogeneous random distribution between 1 and 6 and by comparison to experience you might suspect a dice. Now what of the two things would you consider "understanding"? Like a child watching the experimenter throw the dice and write down the numbers could get the same understanding as the more complex detective work. Is it the same level of understanding though or has the detective work revealed properties of a dice throw that are not immediately obvious to the child?
Or are these further information irrelevant to the problem itself and thus only add unnecessary complexity?
So it would be about the demarcation of a concepts and what is necessary to fully describe and comprehend them. As well as what it means to fully comprehend them.
Also if you'd have ever played with a dice, then just mentioning "dice" would trigger the word cloud associated with that thing, like idk cube shaped, numbered sides, opposite sides adding up to 7, 1/6 probability for each side. And so on.
While if I had to explain to you what a "cube" is, what a "shape" is, what "numbers" are, what an "opposite" is and how probability works. Without any visual aid or prior knowledge and in their full and unabridged glory then you can easily produce something no child is able to comprehend and not necessarily out of a mean spirited attempt to confuse them.
But what if we don't speak about a dice but idk an automobile (a car). Like what do you count as knowledge about cars and what do you consider "the essence" of a car. Like the object/concept that would let you comprehend what is happening beyond seeing part of it or result of it interacting with the environment. Like if I showed you a car, pointed at it and said car and then showed you a different own, would you also identify it as a car, despite being different then the first? What if I took out the engine? Everything looks the same but a major part is missing? Still a car? I mean it's no longer an automobile as it can move itself anymore.
What if I just removed a piston from the engine or an internal part that is crucial for the function but not perceivable from the outside? Is it still the same? Do I understand a car without being able to strip it down to it's vital functionality or is "thing that can be driven" already the essence of that thing?
So even for the most complex subjects you could probably find an abstraction of cutting out some lesser important features, wrapping it in a black box and give it a name and just let people look at the inputs outputs and its appearance, which would be simple, does that mean they understand it? Is what they understand even really what is happening? Or even really what they see?