My opinion as a German writing consultant is: No formal restrictions of word numbers, but support for those who have difficulties to find limits for their work (on ay level). Supervisors can help doctoral students to find the accurate 'size' for their own thesis. Number of words is just one parameter of limitation. Others like scope of the the research question, aspects to cover, quantity of material to work on are more important both for the quality of the thesis and also for the time a doctoral student will invest in the project.
As a supervisor and examiner I have to vote in the 'less is more' camp. I think a great deal of skill is learned by pruning your argument into a lean document. The reality is once candidates move into the 'real' world of publishing in journals and so on there are very real word limits.