wow, that is a strange one. even the bridgestone site doesn't say how they are classified.
1010tires.com says summer as well. they are labeled high performance so i would expect them to be summers.

for the price at costco, i think you got a great deal on summer tires! (though these and all seasons are down right dangerous is the cooler temperatures).
you may have even saved almost enough for a set of winter tires and rims!!

I have a set of Pirelli ice and snow on 18" oem rims I am willing to sell, but I am on the island. $1,200 if I come there, $990 if you come here. they are on the X5 now and ready to test drive. (I will sell since I have a set of 17" rims ready for winter tires as backup.)

PM me if you want.