There is a term “variable program” in your link. When you add peripherals to the chip on the printed circuit board it looses flexibility very fast. The whole system is made to very specific task. But yes, you convinced me that FPGA might be treated as a computer in an extreme case.
FPGA accepts "variable program"s. What you are talking about are peripherals. A CPU with certain peripherals can also be completely inflexible. That is completely outside the scope of what a CPU or an FPGA are though.
