Is this a con?

Looks far too good to be true!
Surely if you're adding enough organic matter to the soil and not adding loads of chemical fertilizers or pest and herbicide, the soil will have a naturally healthy balance of microbes anyway?

There are some microbes that can be really beneficial to plants that may not be present in the soil. I am growing tomatoes and peppers in the same greenhouse border soil every year, so I use a product called TNC Mycorrplus (https://www.thenutrientcompany.com/tnc-mycorrplus) because I specifically want the Trichoderma fungi which can help prevent tomato root diseases.