PhD thesis is taken as the most critical writing assignment of all. This is because there is no way a single mistake could be left in it, as is an indication that student has stepped into the professional world.
Time is the most important thing in this world. This could be proved by the fact that the if it is over then there is no way you can extend it or shorten it if it is prolonged for any of the tasks.
In this manner, from where your recommendation letter is that is from industry or academic and it is not the major issue.