Investment advisors recommend rebalancing the portfolio,for mediocracy?

"78% of Warren Buffett's $369 Billion Portfolio Is Invested in Just 6 Stocks"
"firmly believed that their top investment ideas deserve added weighting"
"Even after Buffett and his team reduced their company's stake in Apple by roughly 1% during the December-ended quarter, it still accounts for 44% of invested assets."
"Even though recessions are an inevitable part of the economic cycle, economic downturns pass quickly. Whereas no recession since the end of World War II has lasted longer than 18 months, two periods of growth over the same span stuck around for at least a decade. Companies like Bank of America should be able to successfully grow their loan portfolios over time as the U.S. economy expands."
"in addition to facilitating transactions and collecting a fee from merchants, American Express is also acting as a lender to consumers and businesses in which it earns annual fees and interest income. During extended periods of economic growth, AmEx's ability to double-dip allows it to thrive
"Coca-Cola also enjoys virtually unsurpassed geographic diversity. With the exception of Cuba, North Korea, and Russia, it has existing operations in every other country."
"The "integrated" aspect of Chevron's operating model is also important. Although drilling generates its juiciest margins, Chevron owns transmission pipelines, chemical plants, and refineries. If the spot price of crude oil declines, the company's midstream and downstream assets act as a hedge that stabilizes its cash flow"
"Occidental brings in the lion's share of its revenue from its upstream drilling segment."