Confusion with Wheatstone bridge resistor terminology in datasheets
But what could be meant by input resistance and output resistance
  regarding the force-transducer?


If the data sheet said input resistance was 350 ohm and output resistance was 350 ohm, I don't think you'd have much worry about that because, 4 x 350 ohms in a bridge gives you that equal input and output resistance. But, when the input resistance is quoted as higher than the output resistance, it makes you think. It's not entirely a guess (because I've come across it before in pressure bridges) but, I believe that extra resistance is due to temperature compensation like this: -



Picture of 4-arm Wheatstone bridge with temperature compensation.

So, from the point of view of the battery, it sees \$R_G+R_C\$. That's the input resistance. The output resistance remains unchanged at \$R_G\$.