I get the sense it arises as more of a response to suggestions that Intelligent Design is pseudoscientific.
Speaking for myself, I wouldn’t respond to the argument by suggesting that science is poorly delimited. I’d respond that Intelligent Design encompases a diverse collection of hypotheses, some of which may be investigated scientifically and so it’s not something that can be dismissed as pseudoscience in toto. Granted, there are a lot of pseudoscientific ideas floating around in that sphere but I don’t think all the ideas are.