A dark pattern implies something that is intentionally misleading. This is just lying. This is not a dark pattern because it’s Worse.
And not all sales/marketing tricks are inherently evil. I don’t think eBay telling you how many users watched an item in the past hour is immoral so as long as it’s accurate.
Lying is fraud, plain and simple, the laws and courts nailed that hundreds of years ago. A dark patter may be fraud, or in some way illegal, or may not, depending on details and jurisdiction. Those details might also include intent. An accidentally bad UI that costs customers money is not the same as a UI that purposefully leads customers to the same situation depending on what you're trying to determine (i.e. was the law broken, or is the UI not good).
That would be the most charitable interpretation.
I suggest you click on the link, they absolutely are lying. They're using JS to generate a random number between 28 and 45. If there happens to be 38 people looking at that flight it's entirely coincidental.