Of course the xilinx SoC is programmable as is the ARM chip used on a RasPi and same for BeagleBone CPU's which are what Bitmain and others used before the s9.

However -- they just handle I/O to the ASIC processors but unlike feeding I/O to a bank of GPU's, the ASIC's have one function and one function only - process SHA256D hashes. That function cannot ever be changed (again unlike GPU's that can readily be programmed to do a plethora of number crunching functions). Those non-programmable super-speed ASIC's are what make any ASIC-based miner regardless of the embedded algo different from the exempt ADP machines. That designed for single purpose function is key to their speed and at the same time their downfall. Ask D3 owners about that.

In this case, that unchangeable core functionality means that by the Rulings any ASIC-based miner has the 2.6% duty assessment applied to it. We are buying these expensive miner to mine with and not to tear apart or re-purpose their relatively inexpensive I/O processors for mundane needs.

edit: In the case of Avalons, at least the controllers - which are just regular, fully programmable and otherwise very nice and useful RasPi's DO fall under the normal ADP exemptions. Just the miners themselves do not.
edit edit: Forgot about the 'data server - no terminal' distinction on the RasPi's so they are not complete ADP's.