You appear to be demonstrating the opposite of what is claimed here: your heart-rate variability seems to have decreased when you were not drinking alcohol.

When I went back to the article to check this, however, I saw that, while the text says that alchohol has "a negative effect on HRV", and their model explains this, the diagram shows alcohol increasing the HRV. As the text's version of the observed results and its explanation for them are consistent, I assume the diagram is incorrectly labelled.

Update: Thanks to everyone for correcting me on what HRV means here.

HRV is not a measure of change in your resting heart rate over time, its a measure of the difference on a per beat basis. Even if your BPM is 60, your heart doesn't beat exactly once a second, it will actually vary in length by some number of milliseconds back and forth. This is what is measured when talking about HRV.

It is believed to occur as the parasympathetic and sympathetic nervous system "fight" over raising and lowering the heartrate. The symbiosis between them lands on a steady rate per minute with fluctuations on a per beat basis.

https://en.wikipedia.org/wiki/Heart_rate_variability

Heart rate variability really does not mean variability in heart rate (such as is shown on the graph linked) it is more at the 50-100ms level in change in timing between hear beats. The graph does seem to show a reduction in RHR but does not address HRV (as I understand it)

That image is of GP's heart rate, not heart rate variability.