Based on Tsuruta-san's description, this is most likely only the kesho (hadori) that is applied in finish polish. From the photo below, it does appear that there is only a sleepy remnant of the original yakiba.
It is possible that the sword was in a fire or exposed to heat at some point which caused the hamon to mostly fade away.
BTW, polishers can do remarkable things to disguise a missing hamon or boshi. This includes inlaying small pieces of hard steel to replicate the appearance of nie. There was one such sword at a recent sword show, where the lower half of the blade had a "hamon" consisting entirely of inlaid nie and a simulated yakiba done through skillful polish.