Sadly it does not use DSA, it just looks that way little, given the way the interfaces are named in the DTS. ipq807x is using a very bare-bones switchdev driver, which fakes all switch ports to the kernel as independent ethernet cards (which they are not, they are part of a common switch) with consequences to MAC learning and other quirks resulting out of that. Contrary to the situation with real DSA based drivers, here the kernel does not get to know about these ports being part of a switch and can't account for the pesky little details that are important to that. While that 'works', it has consequences of stuff that doesn't work as it should be (and the driver itself lacks a lot of basic (checksum-) offloading features).