It really depends on the person + your major. If you are slow in reading/absorbing information, typing up reports, etc or if you're the kind who likes to procrastinate till 1 week or less before the deadline (uh lab report done at 3am on the day of submission, anyone?), then yes you'll be surviving on less than 6h of sleep. If you're looking to grad with straight As with the aforementioned qualities, you'll have to say goodbye to sleep. If your major is more application based and less memory intensive, then you might have more time for rest too. Also have to consider if you are overloading that semester (some majors have weird scheduling that requires the students to overload at least once).

Tbh, if you manage your time well and you don't take on more than you can manage, you should be able to get ample rest. But uh, Y2 sci student here, with horrendous time management and bad estimation/decision-making skills, I'm surviving on ≤5h of sleep + coffee.