Bam bams don't elongate like that. Bam bams are a much orange color as well. I would stop buying from this seller if he is lying to you (unless he also didn't know).
It really depends on how deep your tank is. I would think they'll be fine, and color-up nicely where they are. Mine were near the bottom, under 8x54w overdriven T5 retro's.
If they are Bam Bam's, they will look like my pic above in a few months. They are my favorite zoa.
I'm thinking those are Bambams. You can see their slight "dome" shape (It is just hard to notice it because their tentacles are reaching up). Although washed out, the colors seem to match.