I voice work unique in this regard, do you think?

Not entirely. Stage combat is similar--I've seen people try to explain how to do things like falls and face knaps safely, and that bothers me just as much. You are creating a huge potential for someone to get hurt when they think they know what they're doing but have no actual training.

Sure, many aspects of acting can be improved (I don't know about greatly) just by reading about them. Many can't--even aspects that don't actually create the potential for physical harm.

You can't create a reliable performance just by reading about it, or by practicing alone in your room--you need observers and feedback, especially at earlier stages.

I've gotten good tips about posture just from reading general tips about ergonomics.

You can get some tips, sure. But if you have a back injury and you take the advice of random strangers on the Internet, you're asking for trouble. The same things don't work for every person, and without knowing what's specifically happening in your body advice is just as likely to be dangerous as it is helpful. I have a lower back issue that makes many standard back-limbering exercises damaging, for example--I know it, I've worked with physical therapists, and when I've taken classes that use the exercises I know will hurt me I adjust them because I've worked with trained professionals who have shown me how to keep MY back limber and healthy.

Going out on a limb, I'm guessing you haven't done a whole lot of theatre (5 weeks is actually a relatively long rehearsal period in the professional world, for one thing)--why not listen to the people you've asked for advice, and who know what they're doing, rather than complaining that you're not getting the answer you want?