I would suggest learning standard notation. Tabs are useful (since you often have a choice of what string to play any given note on, but which you choose matters both because different strings sound different, and because some strings will make the next note unreachable), but standard notation has benefits too. If you know both you have a chance of playing along with anyone else - most people will hand you standard notation when they want you to play background to solo, or play with in a group with you (this depends on what type of group - some groups will have tab some will not).
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.
