A growth spurt is only going to last a few days or a week at most so I don't see that a habit is going to be formed. TBH from what I remember of GSs there would be no stopping mine from eating, I mean he would really let you know he was HUNGRY, but it was only a few days (must admit though I never really know a hungry cry it was just something I worked out when feeding him stopped him screaming!).
If it helps to keep his sleep then I think it's worth while, I would let him have however much he wants. Of course if you find yourself doing these top ups in 2 weeks then you'd need to get back on track.