Haven't been checking this but didn't expect Ps4's 2018 to be 1 million higher than Switches 2019.
PS4 had an amazing 2018. Only 1 week below 200k and even that was 199,103. Few consoles have ever done that (Wii, PS2, GBA and DS are the only ones I can image having done it..unless the X360 also did it with Kinect).
However, Nintendo has always been a second half sales player whereas Sony tends to be much more all year rounded. While it looks surprising, it's actually not when you look at the year long trends of the console makers every year.
Look at 2018 first half for both:
PS4 - 7,016,919
Switch - 4,898,946
Now look at the second half of 2018 for both:
PS4 - 10,983,848
Switch - 11,587,952
So despite the 2.1 million deficit at the half way mark, Switch finished 600k ahead in the second half. So it may seem odd that PS4 H1 2018 is a million higher than Switch H1 2019, it's not beyond expected figures given how they sell across both halves of the year.