Total nonsense. I double dog dare you to find any medical studies that suggest stretching prevents damage from a crash or accident. It's not going to make you bouncier or whatever.

I have no idea what operating with greater freedom is supposed to mean. If you're talking about road riding, that's a silly assertion. Maybe it makes sense in something like BMX where you've got to contort yourself into multiple very different positions quickly, but on a road that's not a real thing.