Generally, can one double major in dance and something else?

You heard correctly. A BFA in dance requires about 6 hours of dance a day not counting rehearsal time. There are also dance related classes and core classes to take as well. Your day of class and rehearsals goes from 9 AM to 9 PM in many cases. Then homework in the evening and study for exams. There would be little time for another major. Some do manage to minor in something else but this does take an extra year of school usually. A BA in dance is only around 3 hours of dance class a day along with academics and it is easier to double in that, but it is still not an easy task.

I am not saying that it is impossible to do. It can be done if your school allows it. Your dancing will suffer because part of a BFA is performance and that takes additional time. Count on adding a least a year or more to your schooling in order to accomplish this.