Yes- if I had to guess it’s this. Believe it or not settlement risk is still a thing and we’re still on t+2. Day trading is inherently riskier and it adds stress to the settlement process so this was kind of a no brainer. It basically says you can day trade all you want but put up the money to prove you’re not a complete idiot. Makes sense

This is part of FINRA regulatory notice 21-13, it applies to every broker dealer and clearing firm. https://www.finra.org/rules-guidance/notices/21-13