Can't say what I think here, or end up like Jon, asking for donations.
Sad but true there are no "Polyurethane police" and some companies are worse then others for BS,
Do your own testing. In a quart painters pail pour or leave one inch of mixed clear. Set on bench for month, take puck out of cup and leave for another month.
First week, if clear pulls away from side of cup, that is your shrinkage, a lot will crack in this time also, a sign of poor resin and perhaps cheap fillers to make clear look thicker. (ever noticed, how a cheap clear that is medium solids, looks thicker in can, then a high grade, High solids clear ???Wonder how the math works on that one?)
Some, first hour you pull out of cup, will crumble and fall apart.
A true poly, you can carry that puck around for years and even an inch thick, slightly bend, thicker harder it is to bend but you will see the difference.
Anything else stated is just pure BS and this industry is full of that.