@chriscas and @JeffCampbell
Sometimes it is difficult to understand the reasoning behind something that we don't experience ourselves. If you're a programmer or work with the API, then a number based system absolutely works well and Canvas allows you to use numeric IDs in the calls.
For the rest of us, using a name-based path is human-friendly (it's even called a friendly url) is considered good usability and helps with search engine optimization (although that's not usually an issue within Canvas). Having someone see wave_data is easier to understand than seeing 1241578. It instills confidence in the user that they are going to a page somewhat related to the what the URL says as opposed to some random page number where you have no idea what you're going to get when you get there. From the tech side, it also makes it easier to construct dynamically through programming so that I don't have to look up an ID, I can take my well-formed page name, lowercase it, change spaces to underscores and have the url to use.
On the other hand, I really wish they wouldn't have made this change and I spoke against it (one of the few, I admit) when it was proposed. That's in the past and now people need to figure out how to work with the new workflow after living with the other for over a decade.
I haven't had time to investigate whether deleting a page allows you to remove a redirect and re-use the page. MediaWiki has a way to add a manual redirect code to the page rather so that it can be undone or changed as needed. I don't see any additions to the pages API that allow for this.