Lots of crossposting! I agree with everything CFK posted, wholeheartedly.
For sure, it's a four year old thing.
He could also be testing. DD8 is a big time observer. DD6 is, and takes it a step further, testing.
"I want what I want", for sure. But could it be more in a "so let's see what happens when...."
So you corrected him, good job mom! Internally he might be all: "Well, that didn't go as planned, I'll check that off my list of what NOT to do".
He learned not to do it or at least he learned there will be a consequence that he doesn't like if he does it again.
The moral fortitude stuff comes in later, don't worry!
Also, there's the asynchronistic development thing. He may have not developed his impulse control as well as older DS did at four.
DD8 seems similar in personality to your DS7. Even though I've rarely caught her in a fib, she totally has! She's just not as obvious as DD6 and I also don't expect it from her. She actually probably got away with many more little fibs when she was little.
I think she's pretty much grown out of it, but I fully expect both daughters will lie again at one point or another, especially from ages 13-18, IYKWIM.
It doesen't mean they are rotten kids, just showing poor judgement from time to time.
Remember those teenage years and into college? Even at that age some of "us" were probably fibbing to our parents from time to time.
) to get it." I'm way less understanding about that, I'm afraid!