I do not have much of industry experience but I don’t think it’s possible to skip on to the next phase just to be on track with the pace of the project as it is necessary to complete all the previous stage to its fullest and then move on to the next, as the next stage might depend on the previous stage’s output.
I personally feel the previous stage has to be completed first and then we should proceed with the next once its finished as there needs to be a certain flow and doing two stages at once might as well disturb it, what if one person is involved in both the stages, he has two tasks to take care of and is prone to make more mistakes.