The glitch is in my head

Something that never came up until we had the pandemic recession, because the recession was so short:

The whole year's RGDP for 2020 shows up on the graph before the 2020 recession. When I first noticed this, it really threw me. It's even more confusing (and easier to miss) for quarterly data.

I understand that the 2020 data point is shown at start-of-year. But somehow I missed the significance of that for several years.

Signed,
senile math major