In episode 330 of Semantic Mastery's weekly Hump Day Hangouts, one participant asked if the selection of the GMB service area option has any effect on 3-pack ranking.
The exact question was:
Hi Guys, . . . Need your help with 2 quick questions (smile) . . . (1) Does the GMB “”Service Area”” you select in your GMB listing have any effect on the geographical search area that gets Google to show your listing in the 3-Pack? . . . . .