SK53
Stuff looked OK to me when I got off the tram at Oldham Central about 4 years ago. Because the tram was closed in central M'cr I had far less time than planned for Oldham, so only had a quick scout through the pedestrian bit. The Prince St looks like one inexperienced mapper some time ago. Current imagery shows it as you describe (one of the DG layers). It clearly is not trunk either: perhaps trunk_link or tertiary. I'd suggest going ahead & changing it.

What is true of all the outlying towns in Greater Manchester is that there is very little local mapping activity, so errors or inaccuracies don't get picked up (I just spotted a pub I mapped 4 years ago w/o pub tag: of course it could have closed in interim but is still on FHRS).