There are methods for turning B&W images into masks and, of course, that is one way of creating a LM in Photoshop itself. Another is Greg Benz’s Lumenzia, which I have trial-ed and bought. It is quite clever and very flexible, especially since you can actually adjust the mask itself while creating it, but that just shows that it is relatively easy to create Luminosity Masks for use as adjustment masks in PS.
My whole question was why Topaz, which seems to product all kinds of tools, has never created an app to create luminosity masks. It can not be that it is because PS does that already - PS already does much of the stuff that Topaz has apps for, including ReMask, so I was just curious if I was missing something.