I could flip it over, I think it is symmetrical. I assume he meant for it to be this way because it's the side his logo is on. I did a quick look at the other company that makes one, and their's appears to be similar in nature. These are the two options for this car basically.
http://lrbspeed.com/wp-content/uploa...2/DSCN6724.jpg
Here's a picture of the oem one I think (i never had one since I've owned the car).
https://picclick.com/92-00-LEXUS-SC3...l#&gid=1&pid=1
To be honest I got it mainly to just cover up the bottom so things don't fly up in the engine area, and just protect in general. And also contain any minor leaks and what not. I didn't really get it for any sort of airflow/cooling reasons. If I could have gotten it with no louvers I probably would have gotten that actually. So the actual louver design doesn't mean a whole lot to me. But I do see what you mean. It'd make more sense for them to be sticking outward instead of inward. Doesn't even seem like they do much going inward other than maybe allowing a small amount of air in.