Keeping a neutral spine have been traditionally considered a must in lifting exercises, especially heavy ones like Squat and Deadlift. The reason I've always been told is that it evenly distributes the weight on the vertebrae and also do not squeeze the spinal discs (as opposed to, for example, a spine with an anteriorly or posteriorly tilted pelvis). The latter is the explanation provided by each Stronglift Guide.
However, I've noticed that recently some sources have changed their opinion. This picture shows the evulution of Pheasyque.
Similar opinions about lifting objects with pseudo-deadlifting techniques are provided by this video of Rippetoe, which says that the crucial concept is that the spine must not change its position during the lift.
So, I'm curious to know how much anterior and posterior pelvic tilt in heavy squat/deadlift increase the risk of injury according to the actual state of research. But also I'm curious to knw if keeping a neutral spine is better not only from an injury perspective (assuming that a flexed/arched back is more dangerous) but also from a mechanics perspective (force transmission).