Comment by pfdietz

Ryugu showed an estimated ~20,000 different organic molecules. It's not that surprising that the nucleobases would be among them, along with all sorts of chemicals not relevant to life.

https://www.science.org/doi/10.1126/science.abn9033

In the reference from the link for this HN entry, we see the nucleobases were present at concentrations of about 1 nano-mole per gram (< 1 ppm). They are minor constituents present in a sea of mostly non-biologically relevant compounds.