I have never used the tape. First I impose the edge of one bat over the other and rotary cut so the two pieces now have the same straight edge. Then I triple zig zag the two together pushing the seam together from both sides as I fed them under the needle to make sure the two pieces are butted up together.

I use lightweight fusible interfacing from JoAnn's or zig zag the edges together. Work great for me.

I piece batting using only a zig zag stitch. Never saw the need for tape.

I've seen in on the Quilt in a Day website, I think JoAnn's has it as well as Nancy's Notions, I believe. I personally haven't used it, as I cut straight edges on batting, I use Warm & Natural, I butt the edges together then stitch with a large zig zag stitch and you have a new batting.