How was Kunti ever truthful when she lied to conceal Bhima’s identity?

From Abhiram Gopal Prabhu:
In Kunti’s character in video 2 in the Mahabharata Characters Course, in the same video you mentioned how she said that Bhima has mantras to kill the demon in ekachakra in order to hide revealing their identity and then you mentioned she had never spoken untruth and therefore Draupadi had to marry all 5 sons since it came from her mouth.