If I recall properly, Marcella recommended only the :"Miracle Gro Potting mix".
Other brands and mixtures may have been combined with contaminants.
I have read on other forums that other products may not be as 'fine', nor as conducive to plant and root growth.
Marcella is reknowned as the queen of pot growth mediums , seed germenation, and her love for anti-tree rats(squirrel) pesticides.
I swear by Espoma Organic Seed Starter to start seeds. I would get close to 100% of the seeds sprouting in a short length of time for that particular seed. Pepper seeds are slow to sprout, that’s true, but they sprout faster with Espoma, still slow but faster than others (like never with some). For filling the containers for the plants final home, I only use “Miracle Grow Potting Soil Mix”. They have other types of soil but those words are the exact name of that mix.
I sprouted tobacco seed also using Espoma. I got these seeds from Johnny. Now, that one is different. The seeds look like brown dust. It takes a while, like thinking you will never see a sprout and when you do it’s teeny tiny, just tiny green stuff flat on top of the seed starter and you think you have screwed up. Eventually, it starts upward and grows faster almost every day. Before you know it, you have to put it in its final pot. I did grow them to adult stage.
There are squirrels where I live now and I’ve now got a pellet rifle. Squirrels are murderers of plants and produce. I have pronounced them all guilty without a trial.