Second Largest Ethnic Group by Country

'Arab' still counts as an ethnic group, especially cultural/linguistically (even though culture varies between Arab countries). I would say it is legitimate to call Egyptian or Syrian as ethnic groups but just as legitimate to label Arabs as one ethnic group, depending on the context and how specific you want to be. Copts too are Arabised, and would likely consider themselves Arabs/Egyptians. I agree that the closest parallel to Arab identity is Latin American identity however.

Not sure why that feels odd to you, general consensus is that both of those groups are culturally distinct ethnicities.