IME, neither is taught in the UK PPL.
IMHO, the soft field method is less than effective in avoiding prop damage from gravel, because the maximum gravel damage risk is when the plane is moving forward slowly - the "maximum vacuum" situation.
And that condition is unavoidable... unless one does a gentle low power run-up to maybe 20kt and then goes to full power; that will play havoc with one's calculated takeoff performance, obviously.
That's why, at Elstree (covered in loose stones), I would start the takeoff roll from a spot on the runway which is clear of gravel.