Yes, the split bus panel - three phase above, single below- does exist. One of my customers has one in his restaurant.
You need to look a wee bit closer at the lables. They don't simply say 'no single phase circuits.' Rather, they describe the distribution systems for which the panel is approved; for the 'delta' distribution systems they'll say they're approved as power panels only, or not approved as lighting panels.
In other words, the panel neglects to include the 240/120 delta as one of the approved applications.
I'll see if I can find such a lable and post a pic. Heck, even when younger I needed a magnifyer to read the blessed things!
