Modifying the genetic algorithm
Yes, this is absolutely still considered a genetic algorithm. In fact, it is quite common to experiment with various strategies of obtaining an initial population. As you say, it is reasonable to start with a completely random population unless you have a reason to try something else.

Whether this is a good way to go is anybody's guess, really. It depends heavily on your problem and problem instances. Give it a try and see how it compares to a random initial population. Further, whether this is a modification that is considered fine, trust your advisor more than random people on the internet.