Future capital gains and dividend payments are in no way similar to 401K/tIRA income you've deferred taxes on. If you want to handle the tax on the deferred income as an expense when you incur it, that's perfectly fine, but to compare it to possible gains that may never come is absurd.
Of course they are different. Absurd to handle the way I (and many others do)? No. BTW - who knows how the tax laws will be when we finally distribute gains / dividends. One could argue it's absurd to include our WAG on those as well. But no matter....I've just answered the OP's question about how I personally handle NW calc. You do it however you want, makes no difference to me.