I think the point is that in sport some flexion happens and not to be too worried about the flexion of the spine. Deadlifting with poor form is not what the articles are trying to encourage or promote. That conclusion is not what most people find.
As for specific core training, some of the Gary and Frans stuff is interesting (running with a barbell) but we need to see evidence more on transfer. We all do “stuff” including me to make sure we have done everything we can. The secret is to take away the stuff that isn’t making impact at all and that is hard to do.
Planks are nice, medball stuff helps, but I think sprinting is so fast coordination wise you can’t replicated. Brute force yes…but coordination and getting the work done.