If the price of the parts used to maintain a truck fleet increases with inflation, then it is logical that the price of the maintainers might also increase.
Inflation often results in an overall rise in prices, by raising the price of downstream inputs, such as energy or running costs.

Demanding labour suppliers swallow these price increases and therefore hide the inflation they *did not cause*, while other suppliers are free to pass them on, is to treat labour worse than other suppliers.

Which would be unjust.