Psychology and human behavior are interesting to study. Permitting people to "take longer" and to factor risks into their plan tends to free them up to creatively think of ways to make it take less time - to find technical solutions that also accelerate the schedule.
Yet when you force people to do it faster and faster, ignoring the risks they say are present... well then they tend to find ways to make it take longer, primarily because they never believed it could be done faster in the first place. Yelling louder usually does not generate results.
After 30+ years of working with project teams all over the world, we can report that teams have a better chance of beating their own schedules, but rarely will they beat an imposed schedule. The people that actually do the work will always determine how long that work will take.
There are slight variations depending on the geographic region; for instance Asia has nuances that are not found in Europe, while we see variations between Europe and North America. There is a continuum of "top-downness" from China at one extreme to western Europe at the other, with the North American's falling between. But regardless of the country, few people respond creatively when handed "the" expected result without participating.
Aggressive, compressed schedules that teams don't buy into can only slip, while realistic schedules that where created by a team have a greater chance of pulling-in, because these teams own the outcome and want to do better than they committed (...to themselves).