You posted your question under the video you were watching at the time! That’s where Ginette answered you 🙂. Here’s what she said:
What Jane means in this part is she wasn’t going to carry the thread up the sides as she wanted a clean selvedge. That said, she did tuck her tails with each beginning and ending of colour changes. You do want to do that as well to secure the threads. Carrying the thread up the sides, if you want to see what that is, watch this little bit from Season 1, Episode 3. – carrying weft thread up the side when using colour changes 3.3, 20:12
Sometimes you want to use it, and sometimes not. On a white dominant warp, those colour threads to show up more when carried up and sometimes that looks ok too. It’s what you like in the end. I would start tucking your tails though whenever you change colour, white or the others.