Positioning tags on bearings are not designed to hold the bearing in place. The assembled bearing shells should be a little bit bigger in diameter than the hole in which they fit. In other words, the shells suffer some "crush" when the cap bolts are torqued up. The resulting clamping force between the shells and the rod / cap prevent the shells from turning. The amount of crush is specified in workshop manuals and should be measured as the engine is assembled. If oil supply fails, the bearings can pickup on the shaft and turn with it, even if the crush was within specifications.
John
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