They claim the power per acre is 4x higher than tilted panels. Seems like a stretch, but I don't know how bad the density is in tilted installations. I guess I have seen some where you can drive between rows
Density in tilted installations is quite bad. If you want to capture morning and evening sun at an optimal angle you have to space the panels out a lot, like 5-10 panel heights. You can have them closer, but then you get shading, which defeats the purpose of tilting the panels.