I think it can, and @carverofchoice’s explanation makes sense from an organizational standpoint.
One way to think about it is a document that you create in a modern WYSIWYG word processor. You can go and change elements individually—making the text of headings larger, in a different typeface, and with bold or italics; changing the same kinds of text attributes for each individual subheading in the document; individually bulleting items in a list; etc.—or you can define (or use predefined) element types and then apply styles to the types which are then translated globally, which is a lot less work…especially for large and complex documents. If someone handed you the document where it was created with all of the individual changes rather than using styles, and then you were asked to make a bunch of significant changes to the document to meet a particular need, then you would have to track down and change each thing individually rather than just tweaking the styles that are applied to different element types.
That might be overly simplistic, but I think it might be an apt comparison.
What @carverofchoice is saying about “themes” could be likened to “styles” in such a document, as well.
Part of my problem with the app situation is that it’s not just a text problem: It also affects graphical elements in a problematic way. I can only imagine how bad the experience is for someone with a serious visual impairment.