Why are all the phenyl protons in benzyl alcohol equivalent in the ¹H-NMR spectrum?
You're right, those five hydrogens are not magnetically equivalent. You would expect to see three signals for the aromatic protons.

If you look closer you'll see that the aromatic signal is not a perfect singlet, but is rather more complicated with an additional small peak and a broader base, it is a multiplet. You have three distinct signals, but they are so close in chemical shift that they overlap and result in this multiplet.