You absolutely can use Apple's developer tools without a developer account, and you absolutely can build and run code on a device without a developer account. I'm not sure why Epic claimed otherwise (other than that losing their developer account makes it far more inconvenient), but it's really just fearmongering to try to get the public on their side.
Just because you're physically able to download, install, and run something doesn't mean you have the legal right to use it. The developer tools come with a license agreement in which Apple legally grants you the rights to use the tools, and those rights can be revoked.