What role does bearing play in road network modelling?

Hi. I understand that bearing is related to the direction / angle of the vehicle movement. Based on wiki, https://en.wikibooks.org/wiki/Trigonometry/Compass_Bearings, I got what it is. After viewing this video, https://www.youtube.com/watch?v=T40AMljjgrU I understand what is the bearing between two given locations in a map. It seems to exist a formula to calculate the bearing of two GPS locations (longitude, latitude pairs) out there. I was wondering, what role does bearing play with respect to route modelling? I have heard of modelling road network using limit of linear tiny road network. Is this the only role bearing could play in road network modelling? Moreover, for my understanding, bearing is not in terms of a single point/location, right? Moreover again, lately, I have encountered something like the following which confused me.

@routing @bearing @testbot
Feature: Compass bearing

    Background:
        Given the profile "testbot"
        Given a grid size of 200 meters

    Scenario: Bearing when going northwest
        Given the node map
            """
            b
              a
            """

        And the ways
            | nodes |
            | ab    |

        When I route I should get
            | from | to | route    | bearing      |
            | a    | b  | ab,ab    | 0->315,315->0|

    Scenario: Bearing when going west
        Given the node map
            """
            b a
            """

        And the ways
            | nodes |
            | ab    |

        When I route I should get
            | from | to | route    | bearing      |
            | a    | b  | ab,ab    | 0->270,270->0|

Any comments are greatly appreciated indeed.