Perhaps someone who knows more about the details can chime in, but it is my understanding that UV flashlights shine at specific wavelengths whereas sunlight covers a much broader spectrum (sic.), hence why you get different results. This is true for a lot of the UV curable acrylics, not just the product you tested. The length of the curing time can vary as well, depending on the product, and this one is one of the slowest I've heard of yet. Your hand-held UV flashlight probably did not have the proper range to cure the product. If you look around, you can find UV lights with broader ranges, some even like using UV 'laser pointers' which are supposedly more powerful (and don't make a difference as far as my experiments indicate), but probably easier just to find a different product.

As far as Solarez, really wish they had not learned so quickly how easy it is to gouge fly tiers. What they want to for a 1/2 oz. is ridiculous when you realize how cheap their other products are by the pint or quart. They have a thin UV lacquer substitute that looks very interesting and might serve as well as "Bone Dry" and it costs around $35 per PINT. At that price, it does not have to be identical, just close enough. YMMV.