The TEMT6000 is sensitive and easy to use.
The LED blinking produces a lower average analog input, with steady and off, the high and low. I think it's just a matter of writing a sketch to calculate the average voltage of the flashing LED, giving 3 states to work with for hardware control.
LED during capture is on/off per second, which is quite slow. Sampling sensor inputs over several seconds, adding and averaging should establish the 3 states of operation. No doubt there will be slight variation in sensor values. Perhaps calibration or a range for high and mean values.