API rate limits are more easily enforceable. If they keep scraping there are methods to detect and thwart behaviour. I don't think twitter has the appropriate talent and work environment to allow proper solutions to be implemented. It's all knee jerk reaction to whatever Elon decides.
It's more easily enforced, except when you don't give them enough they just go back to scraping. Or create a million fake developer accounts and pool the free quota if that's possible. These are not hypotheticals, loads of companies have done both against all kinds of APIs over the years, Twitter included.
