Hello Dave,
Since the gyroscope is an I2C device, the sampling rate should be modifiable during initialization through firmware. I have not looked at the code for this device, but the data sheet seems to be missing the the information in regards to the addresses.
One can only assume that the period for the gyroscope was not modifiable in order to meet certain security conditions. Most MEMS cannot be shipped to any destination in the world without security clearance. By having a fixed slow rate, probably allowed TI to get around those restrictions. Something similar to GPS and the maximum altitude for commercial sales.
You can look at the code by either downloading BLE v1.3 or visit the ti.com/SensorTag or the sensorTag wiki http://www.ti.com/sensortag-wiki. There may be some information on the Internet that provides more detail on the I2C addresses for the device.
Thanks,
