Hi SleepDeprived,
Thanks for the update and your comments and insights 
Is this the topper you ordered? It’s frustrating enough when you can’t find out the density of a topper but it’s even more frustrating when the density is listed incorrectly. I’ve seen several examples of this on the Costco website. I’m curious because you mentioned it was made by Serta but Sealy purchased a minority interest in Comfort Revolution and this is the only topper I could see that was available in a 2", 3" or 4" thickness and was listed as 4 lbs.
You can see a video here about the 4lb and 5 lb Bayer memory foam and there are also more about the Sensus and Aerus. “Lively” would be relative to other memory foams that have a slow recovery because it would be anything but “lively” compared to other types of fast response foams such as latex.
They are Chinese manufactured but they are apparently now CertiPur certified (see post #10 here). They should be able to confirm this to make sure.
Phoenix