Do you have a point to make or is is this a display of faux-superiority from someone who actually hasn't got anything to say or any way to back up their insinuations? And you don't know what irony means either.
Empirical results are ambiguous, mostly pointing in the direction that there is no difference in readability between serif and sans serif fonts – and those are often very old studies, done on very old hardware with very low resolutions.
As should be obvious from the Website, iA are also huge fans of and advocates for large font sizes, in this case their body text is over 20 pixels in size. Any aesthetic issues (smushed and blurry serifs) are not really a problem at that size. 10 pixel Times might look ugly (even though it might be as readable as 10 pixel Arial) – its details a blurry mess – but if there are more pixels to work with that’s no problem – especially not with that many more pixels.
Looking at the font, it’s also obvious that it’s supposed to work at the still relatively common low resolutions of, say, laptop screens. Its shapes are relatively simple, the amount of detail is relatively low. It’s only a small step up from the very simple (and also gorgeous) Georgia.
Because of the aforementioned aesthetic problems with serif fonts (blurry serifs at small sizes on low resolution displays) not using a serif font might be a good rule of thumb if you are clueless about typography, but it doesn’t make any sense to adhere to that if you actually know your way around.
And even if you are clueless there is nothing wrong with using something simple and very optimized (also beautiful) like Georgia.
