Flat route to maximize efficency

Maybe put his under the gamification of driving. What are your thoughts choosing a route based on elevation change and slope? I watched a Top Gear episode a few years ago where they debated what was best for fuel efficiency - flat or 'what goes up must come down'. I found a website, https://www.flattestroute.com/, that maps a trip and has elevation and slope but you have to do some calcs to get totals.

My guess is that it is a wash due to commutative law [minus system efficiencies] but wonder if anyone played around with this as part of driving strategies. I have a trip in a few weeks over the continental divide and choosing a route.

Thanks.