As expressions, sure, they are not the same. But "2 + 3 = 5" is a statement about numbers, not about expressions. When you talk about numbers (the object of study), you do not (usually) talk about arithmetic expressions. Arithmetic expressions are part of the language used to talk about numbers.

When talking about arithmetic expressions themselves, you would use a meta-language (e.g., English). The arithmetic expressions would then be called the object-language (the language being studied). All of this should be pretty clear after taking a serious course in Logic.

I am not saying the choice of words is not sensible, I'm saying it it factually wrong.