Not true at all. I have always submitted the time I actually work, and been paid for it. (They do sometimes "suggest" you make sure your timesheet is accurate if it seems like your numbers are way off, but you certainly don't have to.) Granted, you may get fired if you work too slow, but that's the case at any job! And yes, as a beginner, things will take you a lot longer than they "allow", but once you get used to it, the time restrictions are usually not an issue.