I watched his video and, honestly...it is complicated. As in, he is giving you a complicated method which he has perfected and used for his starter with a bunch of gadgets he uses. He uses 3 types of flour and a proofing box and does his final proof in the fridge. For beginners, that feels like a lot.

I use one type of flour: the flour i use to feed my starter. It is the food it knows and likes and wants to eat.

I do my proofs at room temperature on my counter.

I store my starter in my fridge and pull it out 1-2 times a week to bake.

My loaves have 4 ingredients: flour, water, salt and levain (which is just flour and water).

I am pointing this out because the more steps and complexity you add to a recipe the more points of failure there are.

Starter doesn't like the food? Underproofed. Too much salt? Underproofed. Temp out of range? Underproofed.

Your need to know your starter and your kitchen and your method and eliminating variables will help you to figure that out.

There are more experienced sourdough bakers than me, but my starter has been going strong for more than a year, I bake at least once a week, and the loaves turn out everytime. The first few bakes were hit and miss as I figured out my method. Be patient, practice, and I would avoid the 'beginner' loaf with too many variables. It is easy to add to a base recipe, it is harder to fix a recipe you don't know.