They can do infill via the "hollow" feature of chitubox, but you only get one type of infill and no adjustment on it's density. One thing about hollow resin prints though is that you can unintentionally trap liquid resin inside the print depending on the shape. The software includes options to add holes for drainage to the hollowed model but that usually means getting a hole the top of the print since they are done upside down. If the resin is transparent that isn't a big deal since it can be cured but with opaque resin you might leave the nasty uncured resin inside like a toxic piñata.
There is no print time penalty for making it 100% solid. The resin print time is based entirely on overall height of the print so you can print a solid brick the size of the build plate that is 3" tall in the same time it takes to print a skinny little 1cm wide, but 3" tall tower. The decreasing price of resin, it's brittle characteristics, and the added considerations needed to make it hollow have led me to pretty much make everything solid now.
