I think the reason for the terminology shift was to use 5% bleach concentrate to reference a starting point for their 1:10 and 1:100 (dilution) mixtures.

After reading the WHO info I checked the bargain store laundry bleach we have here and it does not specify a concentration, but it is lavender scented I'll be picking up a couple gallons of "name brand" bleach to use as a starting point. The lavender stuff is fine for laundry.