Check out this tweet: https://twitter.com/thy1acine/status/1359308130178404357
It purports that Nublar and Sorna are about the same size nowadays, acknowledging that Nublar was much smaller in the JP era.
I've always thought Nublar was 22 square miles while Sorna was 44+, which Jurassic-Pedia claims as well. I do know that on the DPG website, it stated Nublar was 30 square miles, which is a fair jump from 22, but still not near Sorna's land mass.
The creator gives an explanation in the comments: https://twitter.com/thy1acine/status/1390570789888397314
He used the more detailed map of JW Nublar with the legend in the right-hand corner.