You will know based on what appears when you try to book. If you look at the standard and full size prices, they are always the same. There is no standard car class at MCO and the Malibu or similar that the website shows as standard is in the full size isle at MCO. So if the prices for economy and compact are the same on the website then it is likely they don't have economy cars. When we go through the booking process I notice that the prices are always different, a good indicator that they have economy and compact cars.
If they added economy, it was likely due to demand. With car prices higher, people are looking for cheaper options, so they probably added economy for that reason.