I am no flavour of expert on this, but I don't think they'll definitely be sterile if they're F1. There's a fair chance that they'll germinate, but won't have the guaranteed speed, taste, size, or whatever, that the parent parsnip was bred for. They could be really tasty, or they could be horrid.
If you don't mind risking getting a potentially weak or non-existent parsnip crop, then go for it, I'd say.