This state has some ****** up laws.
Uh no. The laws like this make complete sense, and exist in every state in some regard.
In many marriages, whether it's to decide on where to live or relocate, to run a household, have kids, etc. one spouse or the other sacrifices career progress to varying extents.
In many marriages with "separate finances" they still need to split up bills and expenses. Are those expenses exactly equal? And even if they are, one could be paying for utilities while the other spouse buys the cars in their name and pays the auto loans. So even if they are spending the exact same, one is spending it on things that have retained values and one is spending it on things with zero retained value.
The law exists because when people get married a career sacrifice that impacts earnings and retirement values is a really common thing that is hard to quantify. With separate finances getting expenses exactly 50-50 probably doesn't happen. Having expenses where one person bought things they can turn around and sell upon a divorce while the other spent their money on utilities or food happens.
The law exists because no matter how well people think or claim to be keeping separate and equal finances, they usually aren't, and the laws exist to mitigate these types of problems. For every case where married couples legitimately perfectly execute this split finances approach, there are probably 100 where the kind of monkey business I describe occurs. So yes, the law makes complete and total sense.
And I'm sure your friend will say that he paid 50%, his ex never had to sacrifice career for their marriage, etc. If so, he's the extreme outlier and sometimes laws that make total sense in most cases have exceptions. And in a divorce proceeding if he can demonstrate all these things, he can probably reduce or eliminate any capital gains benefits needing to be shared.