Thanks for your answer. My kickstand opens freely, almost without resistance, to around 20 degrees. Then the resistance becomes much more important. To remove my doubt, I will go to bestbuy and check by myself their sp3 on display.
It may be defective then. It shouldn't open freely at all, it should stay shut tight against the SP3 until you're ready to open it, and then it should require some small effort to open it.