This is a bit long, but these are my thoughts on the FPGA and MCU choice:
Blackfin always gets picked because of high MMAC which is like 400-2000 cycles ( other MCU's don't have it @ 400-600mhz which is the sweet spot... Upper end for ARM MCU is around 500-1ghz. People rarely buy above 1GHZ, and often stay at around 400-700mhz... These are cheaper than TI's sitara line, also doesn't have the multiply-accumulate blocks, so Blackfin is #1 )... Also almost all these low end MCUs have video controllers, most designers do not use them because it's more power draw/disruption/routing ( I'm not going to lie. I agree that you can be one sided and say it's laughable @ 700mW-1W range of MCU. Mostly because this isn't battery-powered )...
Altera FPGA w/ 30K LUT 4/6 ( cyclone), which is above average and more expensive than buying a popular FPGA ( sign of a mistake) $25-50 depending on volume. ( vs $10-25 for 10-22k -> most common cyclone IV ) You'd need a spartan 45LXT to outdo that, which is getting to be pricey/specialized... They must've wanted the gate count badly ( Don't they use LX 25s in rigol scopes? I see it in everything, it's SOO cheap )... The crutch is they can pass DSP between the blackfin and the cyclone IV-E... Cyclone usually has better dsp ( more hard IP for it ) than spartan, but the mid-range on xilinx FPGAs is the winner (ie. Artix or better)... Expensive enough to be near SoC-type FPGA price range. Altera boasts so much about systems integration ( the newer series than this has an SoC line with hard-IP dualcore A9 MCUs, so you can tell what altera wants to sell to it's customers )
The one thing I felt weird about was how many filter caps are in that PSU... That molex isn't even the choice one from their catalog. It must be hard to balance ( Analog devices has a video on why you should keep the power planes as close as possible to the A/D)... I think you should really have the A/D and the FPGA near the front end, and then the MCU behind that, especially because an MCU can't handle multiplexing...
Everything seems confused and vaguely artsy, which attempting an art piece is foolish... The front of it is so stupid looking. It's not really ugly, it's just poorly thought-out and rushed... A lot of those knobs/buttons don't need to be there... In the end the design was rushed with the cheap MAX II Z here which is actually SRAM cell FPGA with flash hiding as a CPLD...( Think of lattice semiconductor FPGAs, or an atmel )... DDS is not the first choice compared to a true synth ( DDS is also hated for high-speed microwave signals too. It's a bad choice beyond 2GHZ ), but I guess it's fine as long as you have proper amplification/filtering...
We aren't in the 1990s, but ALSO I can't say that so fast because... The pin capacitance from using those HUGE and stupid PCB headers on the function-gen probably means none of this stuff winning speed and bandwidth records... I've seen sockets like that where you can do that, but that's for PCI-X and you need at least four 2.x-3.x pericom switches in an array just to deal with all the channels ( Around $7 a switch )... This looks like it doesn't even matter to them LOL...