Well, that's the big question isn't it.
In the soft goods industry there are many different grades of processes used to produce these textiles. Some production requires it to meet higher standards that fit the manufacturers use case.
Such requirements as how will the textile be used, and what conditions will it be subject to will factor into cost. Does it need to stand up to UV exposure, moisture, heat? There's a wide range of textiles for a wide range of applications, from the inexpensive mass products to high end, critical use manufacturing like military applications.
Even though it's my educated option that in hand this boot fabric is familar, and so similar to PU poly/nylon, the truth is... it's still a mystery. And until HT tells us, we do not know it's origins or the coatings's chemical make up. There are the indicators, its flexable, thin, coated, and appears to be a woven synthetic material. We can make observations. It does feel like a cheaper process than more durable fabric made for the outdoor industry.
The rubbery coating is also indicative of a special use case that HT choose. And that's where I think the difference is from PU nylon, the quality of the coating.
While the textiles produced for the toy industry will not have the same standards as expensive, higher end productions. I don't believe that means it's a poor product for the intended purpose, but how many times before have we seen their stuff degrade from use. I would think HT finds textiles that fit their use case, but they've obviously had issues with degradation. I hope they've been doing better with their tex choices.
Good quality PU coated fabrics are generally stable if cared for properly. So, will this scout trooper boot fabric last? Sorry, I don't know. I can only speak in general terms. I'd need to know more specifics from the manufacturer to make that determination. I don't expect HT will release a Material Safety Data Sheet (MSDS) on this stuff any time soon.
With most of this stuff... Handle with care.