The commenter is likely referring to the original S&P 90, which mandated a certain number of stocks in different sectors. At the time those numbers were 50 industrials, 20 utilities, and 15 railroads. The breakdown shifted as the economy changed until the 80's when they did away with sector quotas in favor of rules closer to today (basing allocation on market cap).
Regardless, the S&P 500 also excludes a company like Microstrategy (the company that holds Bitcoin) from their index, had excluded Robinhood for a wile due to missing the profit requirements, and so on. It was never "meant" to cover the 500 largest companies by market cap, and has generally resisted pressure to change that.
Thank you for explaining. People talk about the S&P rules like they are written in stone. There's so much emotion around these exact companies and not the structural shifts that may cause the S&P to adjust its rules. For example, for a time they banned dual class share companies, which would have banned Google from entering today (they were grandfathered on). A ban which they reversed 5ish years later.
They have resisted that pressure historically, and remained fairly conservative. But if these companies stay in the 1T+ range, that's an amount of pressure they have not had in the past. You also missed one of the largest exclusions for a time for profit reasons that's also relevant here - TSLA.
Regardless, the S&P 500 also excludes a company like Microstrategy (the company that holds Bitcoin) from their index, had excluded Robinhood for a wile due to missing the profit requirements, and so on. It was never "meant" to cover the 500 largest companies by market cap, and has generally resisted pressure to change that.