That's completely besides the point. How long does an embedded linux box need to get it's GPU up and ready for number crunching? But yes, FPGAs are best-suited for deterministic low latency stuff.
With the jetsons (agx orin) I have on my desk it would take a bit of tinkering to even get it under a minute.
Absolute eternity by modern computer standards. GPU will be a trillion operations ahead of you before you even start. Or for another view, that's a whole seven frames at 144Hz.
People say FPGAs will be great for many workloads, but then don't give examples. In my experience the only real ones are those requiring low-latency hardware comms. ADC->FPGA->DAC is a powerful combo. Everything else gets run over by either CPU doing integer work or GPU doing FP.