It's a post by a Norwegian author based mainly on data received from other Norwegians, so...
> are these people actually saying they see these images when they think about and use the concept of a year
I do (not a circle but definitely a visualisation I see in my head).
I don't know how reliable the data is, nor how well understood the topic is, but most studies I've seen on this do show the majority of people visually visualise concepts in their head; not universally, there's always people who don't visualise at all, but primary differences discussed in these type of results tend to be whether people's visualisations are vivid or vague or something different.
a) every time they have to operate the "year" concept they see this mental image
b) when they deliberately want to create an image out of the concept of a "year", they see a circle
If (a) I'm probably wildly aphantasiac. If (b) this is only conceptual art.
You spend some decades thinking "counting sheep" was meant figuratively; you discover that was not the case.
Firstly, this study explicitly prompted people first to visualise years as a circle, so there's no guarantee respondents do this every time - so to answer your MCQ, the answer here would most likely be (b).
However, if you were to ask whether people visualise something (be it a circle or some different visualisation) every time they have to operate the "year" concept, I suspect the answer would be (a).
TL;DR: Aphantasia likely
fwiw, Ed Catmull's Disney survey on this topic is interesting (referenced in the wiki article above)
Perhaps it has to do with my bilingual upbringing: juggling with language was my main job for a longggggg time.