Tom did you make that box or buy it? If you bought it, where? Nice set up
His setup appears to be the "dust bucket" (Rockler sells one)
I've used this one for quite a while and is fairly easy (and convenient) to bolt to existing table configurations. Went with this option rather than rebuilding my setup with a DIY enclosure to accomplish the same thing.
Before this setup I had fence only collection, after running large panel raisers there would always be a mess on the floor, the bucket/enclosure configuration substantially reduces that mess.
Ideally, the collection below the table should be done above the motor, I've tried several configs to attempt this but most seem to just 'get in the way'.
The enclosure system does create a 'swirling of dust' environment around the motor but prudent maintenance will mitigate the condition and prolong the life of the motor.
I frequently use a few puffs of air while the collector is running to tidy up inside the bucket and pull the motor/lift out several times a year to checkout and thoroughly clear the 'embedded' dust that inevitably gets into the works.
Heavy use,of course, increases the frequency of maintenance.