Extended single crochet stitches

Dear users, dear authors,
What are extended single crochet stitches? I’ve read that they make the crocheted piece a little more flexible?

They’re also called “single crochet with a foot loop.”
Here’s how to do them:
Insert the hook, pick up a loop (you’ll have 2 loops on the hook), pick up another loop, pull it through one loop (like a chain stitch), pick up another loop, and pull it through both loops.

The single crochet with a foot loop is slightly taller than a regular single crochet stitch. The additional “chain stitch” makes the work a bit looser and more flexible.

I had no idea. Thanks, Ruth