I know covalent--ionic is a spectrum and on one end there's purely covalent / 100% covalent, eg Cl2, to non polar covalent, to polar covalent, to predominently ionic, and nothing is 100% ionic. And there are ranges based on percentage of ionic character, that can be used for these classifications. When we say ionic, it means predominently ionic. Percentage of ionic character is a bit more complex of a calculation than "difference in electronegativity".
It's reasonable to ask if a compound is ionic by which is meant, predominently ionic. OR if it's covalent, e.g. be it non polar covalent, or polar covalent.