It was pretty obvious that Sale had not built the requisite arm strength in Spring Training. His velocity was way down at the start of the season. There was a game when he was at 89. That was eye-opening from him.
Also, let's turn around your argument. If the 4-6 less innings isn't enough to affect their readiness for the season, how could it possibly positively affect their freshness in August and September.
The number of spring innings is misleading. Often the aces are sent to the minor league complex to work against minor league hitters. That would not get reflected in their spring stats. This season, the throwing program was delayed and they just didn't throw off the mound anywhere near as much as prior years. It was a conscious decision and the team did not hide from the strategy. The difference was not just 4 to 6 innings. people here are trying to deny that the coaching staff implemented a throwing program that was designed to limit their mound throwing and it resulted in insufficient arm strength at the start of the season.