You're right, that isn't a small sample. Was there some other factor that was unusual, like using large needles and thin yarn for a lacy effect? It may be that because long scarves get pulled lengthwise while wearing them, that stretching them during wearing encourages the curl more.
Up until very recently, I always slipped the first stitch of each row exactly as you described, and I did once make a stockinette scarf that way. (The only stockinette scarf I've ever made.) It curled like the dickens. No matter how I tried to block it.
By the way, I still slip the first stitch like that most of the time. It makes a beautiful, neat edge. I'm experimenting with knitting the first knit stitch, and purling the first purl stitch. I've read that this can be a better edge for seaming, so I'm giving it a try. I'll let you all know the results!
Keep up the scientific experimenting, Rick! And if you figure out why we're getting different results, let us know!