Yes, no matter what process you choose for your divorce, the California Courts require full financial disclosure of all income, assets, and expenses.

Honestly, I think this is an important requirement even though it can be difficult and cumbersome. In mediation or collaboration where both parties are working together the financial disclosure process can be less complicated because there is reduced time and legal expense sorting through differences in what is included, the values, and agreements related to separate property.
It is time to divide all the income, assets, and expenses you previously had together.
I have yet to see one household magically divided into two with the same income without significant spending changes.
The process of developing a good budget as part of the disclosure process provides great insight into what you have actually make and spend. While it is much easier to just spend, I find that many people can easily adjust some of their spending habits by just seeing where the money is going and start paying attention. Understanding where the money goes also supports making purchasing decisions based more on your goals for your future than on your current emotional state.
An inventory of your assets: house, cars, savings, retirement funds, investments, art, jewelry, and toys along with any debt you might have is important to making decisions about how to divide your property when you divorce.
Even if you are congenially working together, making separate lists then merging them increases the likelihood of including everything on the list. And yes, everything includes assets you had before the marriage, or received as a gift or inheritance during the marriage. In California, it is not typically required to divide separate property, but you must include it on your disclosures. If you end up in court, judges do not look kindly on hidden assets.
The disclosure of assets as required by the courts means that you list them and value them.
Sometimes it is not completely obvious how to value items like pensions, antiques, or tools and equipment. Divorce professionals help people do this all the time, and if they don’t know how to do it, most likely they know someone who does.
So, completing financial disclosures is certainly not something anyone gets excited about, but it is critical information to smooth the divorce process and ensure you know how to provide for your future.