I did a prelim surgery year with intent to do IR, and I did it at a community-based/university-affiliated program which treated us prelims just the same as a categorical surgery resident. I was in the OR every day - logged just as many cases as a surg resident and with the same breadth of cases - did appys, lap choles, and first assisted on ex-laps, bowel resections, colectomies, gastric bypasses and a host of other cases in vascular, cardiothoracic, and orthopedics. So not all gen surg prelim years are scutwork. Because my year was so productive and hands on I can safely say that it has not only prepared me for VIR, but has also helped me be a stronger radiology resident.
But you need to look for these types of surg prelim years. Most of them are not like this and indeed are scutwork.