I am surprised how much people on the forum trust e-mail and SMS. These systems where never designed with the security in mind that is required. Hell -- faking the from address on an e-mail doesn't even require a lot of technical skills just an open SMTP server.
Globally there has been a move away from SMS/e-mail for verification, and not just for banks.
So maybe your gmail address is well protected because Google implemented all kinds of additional security on it. Your local
myusername@randomisp.co.za DOES NOT have the same security. Hell - SMTP is not encrypted by default so a lot of people are vulnerable from network sniffing. And even when it is encrypted there is no globally rolled out trust network.
SMS -- I can't believe nobody acknowledge the variety SIM swop scams we had over the years where bank accounts have been emptied.
And with both of those mechanisms - even people who think they are competent can fall for a well executed phishing attack. ( do this quiz without peeking -
, read
https://www.troyhunt.com/humans-are-bad-at-urls-and-fonts-dont-matter/) . Most "experts" here don't even know what a homoglyph is (because they are so used to ASCII, and I don't think I have ever met a unicode expert in my life).
Using the App enables FNB to have a single communication channel which they can reinforce the right behaviors on their customers. Got and e-mail or SMS -- just ignore, always look at the app.
Also the app allows for other telemetry data to prevent fraud. E.g. - device identifiers, location etc.