H NMR of 1-bromo-2-methylbenzene. Why are these hydrogens chemically equivalent?

Chemdraw uses a similiar, but more advanced, system and here the values lie close together in the prediction.

They are not. It’s just that the combined effect of the bromo and methyl substituents gives them very similar chemical shifts.

Plus splitting pattern is going to guide someone examining HNMR. Do note these will have two different multiplets likely to overlap. The aromatic region of a spectra for some compounds can look very messy and not so well resolved.

If you look at the overal structure, you will see that the molecule is unsymmetrical. Therefore, these protons will not be chemically equivalent

Here’s a resource that goes into more depth than I want to get into here.