Bare neutral to subpanel in detached garage
The Power Company did that, didn't they? :)  They gave us a very similar setup; thru lugs off the bottom of the main panel, back up the pole to another pole to another panel.  They're installing that according to NESC, which is their electrical code.  Not ours.
Yes, in that case, you need to install the garage exactly like a whole separate service -- neutral-ground bond in the panel, 2 grounding rods etc. (assuming the concrete guys weren't kind enough to give you an Ufer ground).  And this also counts on this being old enough to be &quot;grandfathered&quot;.
The bare neutral is not a big concern; that's just how pole line is done under NESC.
If you want or need to modernize that, yes, you'll need to go 4-wire, and if you ask the PoCo to do it, they'll look at you funny.  They do have 4-wire; they're just not used to putting it on the truck for residential jobs. It's used to serve 3-phase to businesses.