Thts not dangerous at all...It allows you to press the brake hard enough to apply the brakes and then release the pedal and the brakes continue to hold until you press the brake again or press the accelerator pedal.
https://media.ford.com/content/dam/...016/2016_Lincoln_MKX_Auto_Hold_Fact_Sheet.pdf
http://www.fordservicecontent.com/F...tleSelected=G1767714&topicHRef=G1767715&div=l