As far as I always knew, the category of lebo gas bo is much stricter and this category has many more restrictions in hilchos yichud.
Indeed by Libo Gas Bo the restrictions in hilchos yichud are stricter.
And the Shulchan Aruch (E.H. 22:8) and the Aruch Hashulchan (E.H. 22:6) present examples of a man and a woman who grew up together or are related – such as cousins. Libo Gas Bo also applies to a man and a woman who are very friendly with each other, such as those who work together in an office or if the man and woman dated. Rav Shlomo Zalman Auerbach (cited in Nishmas Avraham 3:94-95) and Dvar Halacha (7:17), state that Libo Gas Bo applies even if the man and woman have only had minimal interaction such as a woman who has visited a doctor a number of times or a man and woman who had some business dealings together.