Earlier quoted context omitted.
I mean it sounds like if you could get your hands on this yeast you could actually make psychedelic beer (or bread).
I think the method uses some special enzymes that can only be really be used with yeast. So yeast is just a supporting role in the operation and the enzyme is the star. They say they tried to get E. Coli to operate the enzyme (E. Coli is used often to make all kinds of drugs, like insulin) but it didn't work and got yeast to work with it.
So instead, they put the same genetic material into yeast which already had the necessary metabolic equipment to make the entire compound "de novo" (i.e. from scratch - just add sugar and yeast nutrients and it pumps out psilocybin). The downside is that the yeast's metabolic pathways chew up about half the product, so there is still work to do on making it more efficiently, but at yields of 600mg/L it's not exactly a bad start. (For reference, depression researchers tested the compound at dose of 30 mg for a 155lb man and it yielded psychoactive effects.)