Crochet Invisible Decrease

I've been crocheting flower petals and I have a few more to do. I've been doing it this way

How to Crochet - Invisible Decrease - YouTube

and another video

Invisible Decrease Crochet Technique (inv.dec) - YouTube

but I thought I'd try making these Festive Crochet Friends: Christmas Decoration Pattern - Dora Does but after rnd 12 it says to fasten off and use the invisible join to weave in your ends. (click on the purple words to see festive crochet friends or copy and paste it into your browser (which my husband said is a safer way to do it).

Then I watched this video How to create an invisible join with crochet in the round - YouTube

I guess a invisible decrease and a invisible join are two different things.