I didn't think that was true because the older weaker cheap high tensile steel frames with low carbon were exceptionally easy to weld and could be welded by anyone with basic equipment but these newer high carbon steel frames are harder to weld and need better equipment. The way I read it is many of the smaller bicycle factories which weld themselves are still welding low carbon (easy welding) high tensile tubes for their frames but new improved processes allow for welding high carbon steel frames with heat treatment to enable a cheap not too brittle frame of decent tensile strength. I didn't think 1010 to 1018 were considered high carbon steels which are the steels used for more basic high tensile bike frames of the past I thought they were low carbon steels. 1045 is classed a medium carbon steel and beyond that perhaps somewhere around 1065 we have high carbon steels. So I wouldn't of thought they were the same. I think there has been some movement in manufacturing towards using high carbon steel in bicycle frames thanks to new welding equipment and processes. Weight of steel frames has been dropping for these cheap steel frames and they are much more competitive in weight now.