Sure, just use 1 core to turn Arduino/C++ into whatever the rest needs.
I have a hard enough time programming for 1 processor, I can't imagine writing code for 1000 that has to all interact.
What's that thing do for IO? I don't see 1000 IO pins to interact with the outside world. Is it multiplexing IO pins somehow? Maybe some big I2C or RS485 type busses internally? Every 50 or 100 processors shares a pair of IO pins for serial comms?