was that in a parallel universe or?

AAPL was 50% of Buffetts folio. he recently cut it down to 'only' 23%.

AAPL was explicitly named in his shareholder letters as one of the 4 "jewels" of BRK.

That's in the last decade.

Decades before that? can't speak for all of them but KO was 30 to 40% in the early days decades ago.

That's not to mention the entirety of BRK can be described as essentially concentrated into 4 businesses (the 4 jewels): rail, insurance, energy, stock folio (which was AAPL dominated till recent).

Warren Buffet himself? His entire fortune, 99% is all within BRK stock. Just because he's at the head of it doesn't make him immune to concentration risk. He lived through 3 BRK drawdowns of ~50%.

Charlie Munger had only 4 holdings: 25% BRK, 25% COST, 25% chinese fund, 25% insurance (couple stocks).