I don't think I can extrapolate your point. It all boils down to what the student wants: quick results or to actually learn OpenGL?
All I'm saying is that if you want to learn OpenGL, there's little point in spending time on de facto deprecated functionality.
Students will never use the OpenGL immediate API in a production coding environment.
One of these is a much better didactic stepping-stone than the other.
In C, the canonical hello world example can help teach about the program starting point, return codes, argument passing, and IO. This extremely simple program can help the student learn these core concepts, even if in practive their program may ignore all of that for main except what the instruction starting point is.
Was the exercise pointless, or did it help cement core concepts which may help later?
No, not a single one.
immediate mode had gl_Vertex, gl_Normal, gl_Color. Those are all gone. immediate mode had lighting, that's now hiding the fact that modern GL has no lighting, you have to write it yourself. Old GL has no normal maps, no opacity maps, no specular maps. Old GL had a matrix library. That's gone to.
You learn almost nothing from immediate mode GL that is relevant to modern GL.
You could argue you learn about some common 3D concepts like a projection matrix and a model matrix but since you don't actually work with the math in old GL you aren't really learning anything more than you could learn from any other 3D library built on top of GL.
Because it lets them get feedback along the way while exposing them to some of the concepts they will be using later?
Taken to the extreme, that statement is the same as saying 'If your students aren't ever going to print "Hello World!", why ever use that string? They should be finding something more relevant to their eventual goal.' That is, as stated, extreme, but you can extrapolate my point from that.