BRK is now (since the last 10-20 years) large and diversified enough that it more or less tracks the S&P 500 and the overall stock market. There isn't some genius trading strategy in there. Buffett himself tells everyone who will listen to buy and hold a diversified index fund for a long period of time.
BRK is like a conservative S&P500. It offers enough diversification off the "total market" funds for me that I invest a small but material portion of my "safe money" with them.
Sort of like holding boring dividend stocks without the dividend.
Berkshire's cash holdings are pretty different from an S&P 500 index fund.
BRK and VOO have a correlation of 0.7 over the past 5 years. That's high enough that they have been relatively similar, but not so high that I would really say it "tracks" it.
Of course, no one knows the future so who knows if this will continue.