Very interesting question and not very obvious. As can be seen from the picture, LAB's reduce only tertiary amides. It is stated in the publication(1) about LAB reductions:
LAB reagents do not
reduce primary and secondary amides even in refluxing THF.
In the same publication it is provided reason for different outcomes of reductions. They say that:
We found that the outcome of these reductions depends on
the sterics of the amide as well as of the LAB reagent
Which means that if LAB and/or amide is sterically hindered it can't interact with nitrogen like in compound 5
In lower part of the picture is described reaction where more hindered LAB leads to amine product 9
(1)Pasumansky, L., Goralski, C. T., & Singaram, B. (2006). Lithium aminoborohydrides: powerful, selective, air-stable reducing agents. Organic process research & development, 10(5), 959-970.