Good question! Your perspective on that might differ a lot depending on how long you've been on the internet.
In recent years, every major messenger (WhatsApp, Telegram, Signal, ...) has been doing it this way, linking your phone number to your identity, so your contacts are automatically discovered from your address book (and reciprocally, people who have your phone number already will find you easily and as soon as they install the app you recommended to them). If that's all you've ever known, not only is that not a bug (or rather, a major privacy and identity linkage breach), that's a convenient feature, and you kind of expect things to work that way. I personally don't like that (and I'm aware of being a dying species).

Now, regarding Prav, please don't use it (for the time being, at least). As far as I can tell, this is a fork of the Conversations/quicksy.im XMPP clients (Conversations being the original work, and Quicksy being a derivative by the same author using the phone number discovery / easy onboarding approach discussed here). Unlike the original which is very safe and reputable, whose author is known and very active within the XMPP/security communities, and whose hosted service has years and years of excellent service and uptime under its belt, this one comes out of nowhere, from an unknown contributor (afaict), has no funding model to suggest it being sustainable, and worse, no rationale as to why it exists in the first place (why would it be chosen over the original). So, my recommendation is to stick to those.

Back to the original question, thanks to Quicksy.im having been around for several long years already, the debate of having phone numbers being used for identification on XMPP is not really something new. Having been there for a very long time and seen the before/after, indeed this has enabled some of my current contacts (who were already users of other services like WhatsApp and certainly didn't mind) to get on board a bit more easily. They are not the majority, so, and in all, I'm glad that the option exists, it's not as big a deal as it might seem for XMPP in general.