I don't see the point of paying all that money for a wheel bearing spacer when the front bearings are designed to have end float, this allows for expansion when hot.
I share your doubts, I worry about attempts to modify original designs because I am not convinced that people actually understand what they are modifying or doing.
It all depends on whether the movement this product is designed to remove was meant to be there, instead of a design flaw that should be engineered out.
I am sure one of the more knowledgeable posters will be able to tell us which it is.
They are used as OE on MGB's and many other cars. It does really not take the end float out, but locks te inner and outer races together so less movement and risk of wear to the stub axle. They are undoubtedly a good thing, and not used at the factory to save time/money.
There are many owners using them on a variety of Triumphs (including some fussy people) who are very pleased with them. These are cars used for long distance CT events, so a fair test.