Not true. If the cams are not exactly centered on the followers and you undo the tensioner the spring pressure will move the cams. The cams are on different centers so it is nearly impossible the get no pressure on the cams without rotating to tdc. It is soooo easy to get tdc why take a chance by not doing it?I don't think so. As long as the cams are still bolted in the only pressure the chain's under is from the tensioner itself. I believe TDC only matters when you're checking valve clearance and changing shims.