As you would know, most SM's start the show & Acts religiously by the clock anyway.
However to be able to advise that the Act took this amount of time or that, as a production guide. Can be another story all together. Especially if it is the type of show, where the SM is hard pressed to get time for caffeine or a smokeo, during interval or even right after the show.
Much the same with electrical service calls, where one can be too knackered to remember the exact time anything took & resort to guestimations when filling out the job card or invoicing later.
Of course systems are place normally within the service industry, but from experience even in the best organisation depending on work load, they are left to memory & empirical knowledge of the time it normally should take to perform the task.
Much the same with theatre, except in comeatre, where the timing of the performance & completing show reports. Are something that most SM's never indulge in & no one takes much heed of anyway. Which is more the pity, as the vast majority are doing it, as the pseudo prompter. Or given the job because they missed out on a part on stage &/or there is no one else to give the cues. Thus not working or held in the esteem of their position & also receiving constant interference from the director or others, who should have evaporated at the dress rehearsal.