I bet Don can speak to variations in paper stocks better than I can, but this is probably more a question for USPCC than me. Tendril is on Bee stock, that's what is on my contract and what I specced. I believe that Tendril is the first deck that is black, on bee stock with magic finish and I'd guess that variations you see in thickness come down to the batch I paper used. It's impossible to create paper that is 100% identical every time, but I'm pretty sure they didn't swap out the stock and not tell me. 
The deck does feel an handle quite different from any other deck I own, and I've gotten lots of feedback along those lines. I think it ended up being a pretty unique combo
No matter how many times I have this conversation and post all the info, it seems people either forget or don't pay attention...
USPC has all KINDS of variances in their stocks. Buy Bicycle stock one month and the same stock in a different month, and you're probably looking at two very different pieces of paper.
They do have benchmarks as to what a particular stock is supposed to be, but they allow for a fair amount of variation.
Paul, there is that point that you stated the contract read that you were getting "Bee stock". Bee stock and Bee CASINO stock are two different grades of stock. Both are good but Bee Casino is more durable and stiffer. Please look at the contract and verify if the mention of "casino grade" or anything similar appears there. If not, you likely were given standard Bee stock.
But even with that, even using identical stock batches to make a card, the print process itself creates differences. Zenneth Kok mentioned on this board that he noticed a distinct difference between his Gold Seal New Fan Backs in white and black. The most likely cause would be the different levels of ink saturation. This is not just a Bee or Bee Casino stock deck, but it's also got a LOT of ink on BOTH SIDES of the card. In fact, Paul mentioned that the edges of the black field fade out to gray, meaning that it's possible that every square millimeter of this deck has ink on it.
Comparing this deck's thickness to an Ohio-made Shadow Masters is ridiculous. They were using UV500 stock at the time and ALL their decks were coming out thick. I think this trend toward thick decks at E ended after Arcane.
If you want the closest thing possible to an "apples-to-apples" comparison (and it still won't be 100% accurate), you need to compare the Tendril to the only CARC deck made to date with Magic Finish - the Black and Silver Acorn back. (In fact, the Ivory version of that deck is the very first ever to be Magically Finished on a smooth stock.) And even that wouldn't be totally accurate, considering the CARC deck has much less ink on the front and somewhat less on the back of each card.
But before you do that, go into your collection and grab a handful of Bicycle Rider Backs. We know you have them, everyone does! Get decks that are either new-in-package or recently opened and lightly used, and as many as you're wiling to open in the name of science. Start stacking these decks side by side and compare them. If your collection has decks from different batches, all the better - they would have different numbers to the right of the letter code on the Ace of Spades. Be really scientific about it - bust out a good ruler with metric measurements or better yet (for those who use and can afford them) a good set of calipers that can measure in tenths of a millimeter or smaller. You'll notice variations from deck to deck, almost certainly - especially in decks made in different batches.
Remember this important little fact - USPC has practically no control over the precise quality of the paper they receive from the paper mills - and they don't source from just one mill. There are countless factors that can affect its characteristics. You can think of it like top-notch unblended wine batches made from the same vineyard - year to year, various factors can alter the wine's characteristics - and they'll keep on changing in the bottle over time. Paper is an organic product, and as such it varies, and just like the wine, even in storage its characteristics can change. Now that recycled content appears in some percentage in practically every batch, the variances will become even greater (unfortunately tending towards lower quality). They do try as much as possible to reduce these differences, but they still occur.
And again, just like the wine, it will continue to change while sitting on a store shelf, sitting in the back of a tractor trailer, inside your post office or in a box in some reseller's warehouse, and even when they're in your possession. If they didn't change, cards taken out of a sealed vintage deck, freshly opened, would look practically identical to modern ones.
OK, I think that's enough windbaggery for now. Questions?
