There is a theory that when welding on steel with bearings, an arc could create a spot on a bearing that would ruin it. It was thought that this arc would occur on any bearing between the ground and the welding point. In all the years I worked in the maintenance field, I never saw that happen, not even in babbitt bearings. Good welding practice would be to attach the ground as close to the welding point as possible.
2013 Crusader 330 MKS
2013 Chevrolet Silverado LT 2500 D/A