I agree with you guys.
I also have the spec sheets for a number of previous Ford model years on the E350 and E450, to compare technical differences. Too bad that information is not available for the new 2021.
As of late, every Phoenix Cruiser, regardless of floor plan, is built on an E450. From 21 feet to 32 feet, they get the same chassis, just different wheel bases. Their shortest model 2100 must bounce, shake, and rattle down the highway quite a bit. If I owned such a rough-rider, I would surely get the springs modified or replaced to work with the "actual" load.
The spec sheets we are referencing here state a 2007 E350 has the exact same front coil springs as the E450. I just replaced our front springs to a lower-rated version. It explains why we had a rough riding front axle all these years. It's all better now. You can read about it
HERE which includes many pictures.