When the railway starts up, the PC control software "Traincontroller" needs to know the position of all points. It remembers them from last time, but they could have changed if the railway was used without the PC connected.
The Digitrax system includes an "interrogate" process at power up, which causes all LocoNet devices to report their state. Unfortunately Traincontroller ignores this information at that stage, for reasons that aren't obvious! However, Traincontroller has a "track power on" pushbutton on the toolbar. This causes all the positions to be queried again, and the program then knows all of the states - even if they changed after the program was last run.
The DAC20 has a unique capability: it can generate the necessary "Turnout Feedback" messages even if the points don't have a feedback microswitch. It remembers all the positions even when power is removed, and it can generate the messages from the "stored" information.