They don't, while timing certainly benefits, and potentially was triggered by them and OpenAI and Anthropic IPOs, these rules are not specific to only apply to SpaceX.
FTSE Russell (Russell 1000/2000 etc.) Adopted "fast entry" for large IPOs. Eligible companies (investable market cap above Russell Top 500 cutoff) can join after 5 trading days (previously quarterly rebalances). Also eased float rules with carve-outs.
https://www.lseg.com/en/media-centre/press-releases/ftse-rus...
Nasdaq (Nasdaq-100): Effective May 1, 2026, top ~40 market-cap companies can enter after 15 trading days (previously 3+ months). Adjusted low-float handling.
https://spotgamma.com/spacex-ipo-index-changes-spotgamma/
S&P Dow Jones (S&P 500): Reducing seasoning from 12 months to 6 months for megacaps and waiving the 4-quarter GAAP profitability requirement for large issuers.
https://www.wsj.com/finance/stocks/stock-indexes-are-contort...
So the question remains, why do they warrant a rule change?