We actually have a lot of studies where even standard 10mg phenylephrine taken alone outperforms placebo: https://pubmed.ncbi.nlm.nih.gov/17692721/

Note that Figure 3 also mentions the Tylenol combination effect and even shows how 10mg Phenylephrine + Tylenol performs somewhere between 10mg and 45mg of phenylephrine.

The article author just cherry-picked the one study where phenylephrine performed the worst. Cherry-picking a single study to support a conclusion and ignoring meta-analyses would normally get someone torn apart in the HN comments but apparently everyone loves pseudoephedrine so it gets a pass.