I think many of the non-tubeless WTB tires are wire-beaded versions of their TCS tires sold direct to bike manufacturers that they don't sell retail.

For instance my bike came with non-tubeless, wire-beaded WTB Riddlers and I don't think that tire was ever sold retail.

I've struggled enough with installing tubeless compatible tires tubelessly - sure wouldn't want try to make a wire-beaded tire tubeless.