Guitar tab is uniquely suited for exercises because it directly shows which string and fret to play, which is important since the same note can be played in multiple positions on the fretboard, unlike an instrument like the piano where std notation does show you exactly what to play. It also clearly communicates guitar-specific techniques (bends, slides, hammer-ons, pull-offs) that are awkward to represent in traditional notation. For exercises specifically, tab shows you where your hand should be positioned on the neck, making it easier to develop proper technique and muscle memory.
BTW the original comment didn't make sense since the app does support tab, just wanted to make this point. Also not saying that learning std notation isn't valuable although many excellent players never learn it.