This is nothing but a bad strawman from start to finish. Sprints are not made to help organize things, they're a tool to get more predictable deliveries. Their very short nature forces participants to construct tasks that are easier to estimate and therefore complete on time with a higher probability. This certainly adds overhead to an idealised scenario where people take the shortest reasonble route often enough and…
It's all about how everything is implemented. I've worked in places where sprints were hard deadlines and there was no acceptable reason for missing said deadlines. We worked 12-15 hour days, including working weekends to try and meet our release schedules. Run into a blocker? Too bad, should have seen it coming during our scrum meetings and follow-up refinements. We engineers had two business analysts, a scrum maste…
One of the things that usually happen when they push and push and push for some feature to get rolled out in the next quarter is that it often turns out to be a gigantic flop. Engineers are forced to spend hours they can't get back at the whim of management for something that was a complete and utter failure. I could imagine few things more demoralizing than this.
Agile is really meant to be about self organizing teams that take ownership of their own work and deliveries. The scrum master and product owner are just there to facilitate that.
When a team hits a blocker on a tight schedule -- particularly across third party teams, it's up to the management to figure out a solution -- even if it means gasp delaying the release by one sprint.