To your - bad - analogy: If MS was selling templates created in word by you to a marketplace, you can bet that GST would be paid on them by the consumer to MS.
Consumer pays GST to MS. MS pays GST to a GST collecting template provider. MS and template provider both pay GST to government, but MS gets an input tax credit for GST paid to template provider so that government doesn't double dip.
This is what uber should be doing with their drivers but they prefer to have prices 5-15% lower than their competition by applying their own legal interpretation to Canada's tax laws.
Now, the major issue here is that if the app creator is making $30K+, it is THEIR responsibility to charge GST, which means that if there is no mechanism to charge in addition to the price, it's automatically inclusive. The CRA doesn't care how you collect the tax you owe, they just care that you pay it.
For a vast majority of app creators, $30K probably is a target they are on the lower side of, but I'd imagine people making a living on the apple store, the GST is coming out of their revenue directly. At least, that's how CRA would look at it.
Now that being said, CRA might be treating this entire industry as an undefined gray area for the time being, particularly since they are getting the GST on the final sale by apple, but I don't think that will last long.