That's only true for the first year, and only if you fail badly (ie. stop doing any work at all) -- unless they changed it very recently.
That's from their page, for me this looks like you have to pay it back if you, for example got bad grades, in fact I can ensure you, that the limit is 50%, if you screw up in more than 50% of your courses, you are done.
In general, you need to complete around 50% of your courses to continue receiving the stipend next year, but you only need to pay it back if you drop out in the first year and have completed less than 25% of the courses. (Exact numbers depend on the type of program you attend)
Details are here: https://www.stipendium.at/studienfoerderung/studienbeihilfe/... https://www.stipendium.at/studienfoerderung/studienbeihilfe/...