My view of Walz's rural prowess is based primarily on learning about his tenure in the 1st Congressional District, where he beat a Republican incumbent and held on to the seat for a decade, in a district that reverted to Republican representation when he left Congress in 2019 to run for governor.
In statewide races since then, its difficult to compare apples to apples. Walzs appeal would seem to be pretty different from that of AG Keith Ellison, and Steve Simons opponent for Sec. of State in 2022 was the election denier Kim Crockett, so Fear Of The Crazy may have inspired some crossover votes for him (my uninformed armchair analysis). In Pennsylvania, Shapiro in 2022 did well around the state, although his opponent was Jan. 6 insurrectionist Doug Mastriano, who fortunately turned out to be a beatable foe who was apparently radioactive to many in the Republican establishment. (https://www.nbcnews.com/politics/2022-election/uphill-slog-gop-republicans-start-fleeing-mastriano-shapiro-pa-rcna37018)
On the Ezra Klein Show podcast (https://pod.link/1548604447) the other day, Walz admitted that Minnesota is more politically polarized today than when he was first elected to Congress, so it could be that the path to Dems winning statewide is now similar to other states (such as my home state of Georgia), where sheer numbers in metro Atlanta and other large-ish cities, plus (in the case of Georgia) turnout in majority Black counties in the Black Belt region, put Biden-Harris over the top in 2020.
Whoever gets the VP nod, I hope the ticket will be able to move beyond that formula somewhat, because a) its always better if you get buy-in from various constituencies and b) in a close statewide race, losing by less in a bunch of rural counties can help boost the numbers needed for victory.