Leg 5 is going to be a chocablock full leg, I am sure they needed to get them there to get things rolling early. It may be our most visualizing striking leg of the season!
But is it worth ruining the previous leg? That train ride to Chamonix made nothing else count besides the teams' physicality.
They could've made the pitstop in Geneva, made the leg KOR and then teams immediately take the train. If needed, there could have been an HoO somewhere in Chamonix. Here's your solution -- nothing changes for production, but at least the Swiss leg and the efficiency of teams has some bearing on their placements...
And if they badly wanted to eliminate a team in leg 4, they could've introduced a new twist - a KOR leg with an elimination.
Or if they did not want a KOR on this one, they could've made a longer pitstop in Geneva, so that teams arrive in Chamonix whenever production wants/needs.