This piece isn’t difficult if your fingers are articulating properly, so Grade 4 is just about right. It should be practiced so that the fingers pull into the palm, very relaxed, the notes should be even and flowing (lke a fountain!), and the melody should be brought out.
My second-year adult student with a piano background is playing it and doing quite well with it. I don’t think it is too advanced, but I am not familiar with those level numbers. You learn downward arpeggio technique with it, but it doesn’t demand melody at the same time like La Source and other etudes, so I think it is ideal for a first arpeggio piece.