The "minimum spring pressure" issue is with regard to the usual camshaft break-in cycle of 20-30 minutes at 2000 to 2500 rpm. That is not to say that lower spring pressures don't always result in a camshaft that is not broken in. Often in that case a longer break-in cycle is required. I've never run accross written specs that say this either but have had dialog with camshaft designers who do.