It was a measure of concern for me when I initially saw the Natively listing, but the chapter preview doesn’t seem to match that rating. Somebody who has read further in the manga might be able to judge a little more effectively, but especially when looking at what it’s being compared to in order to achieve that rating, I think it’s a case of the level getting artificially inflated a bit. (I also confess to being confused by the one rating which places it as harder than 五等分の花嫁, because nothing in the preview gave me that vibe 
).
My overall thoughts:
I think both Hunter × Hunter and Cells At Work!! are going to be on the “upper end” of difficulty for this club, but I don’t think either are going to be too much for the club. Reading through the preview, I had an easier time getting through the preview than my first encounter with 三ツ星カラーズ, for example. Some of that could be more reading experience, but I also think that some of it is just the writing style. This manga feels more immediately accessible, whereas 三ツ星カラーズ required some time to get used to.
Though, again, this is all based on the first chapter preview on Bookwalker, so maybe there’s something later on that warrants the higher rating that is given by Natively.
Tl;dr: Given that many of the higher leveled “easier than” books that it is being compared to trend towards being light novels which are in the mid-30s, I think it’s just bad comparisons inflating the score. This may end up being on the upper end of the difficulty scale for the ABBC, but I don’t think it will go outside the bounds of being doable.