Important to note, Penicillium mold is not Penicillin. Bread commonly available in modern grocery stores is often not made the same way as back then, and will be growing and carrying other pathogens which you don’t want to be getting into an open wound. Penicillin, the modern medicine, is highly processed, and impossible to manufacture without what amounts to a laboratory.

They covered this a bit, at the end of the article:

Furthermore, Egyptian bread was leavened without yeast, in contrast to ours, which typically contains yeast. Therefore, using our moldy bread to cover wounds is not recommended. Our bread contains numerous chemical elements that, instead of aiding in wound healing, could worsen the condition and potentially lead to more serious pathologies. Additionally, Egyptian bread was manufactured using clay pots baked on hot ashes, while our bread involves machines that, despite hygiene efforts, may harbor microbes or bacteria.

I got interested in how to make my own modem medicines because there’s a nonzero chance I’ll need to know how in my lifetime, so learning how hard it is to refine was a great disappointment.