Nope ...totally wrong ...
What's totally wrong?,the page count?
You can see for yourself,the majority that end under 25 chapters tend to either be quite tight in their lore or are rushed,and there's plenty that end with less then 15 or even 10 chapters whilst still having a 20~ page count per chapter.
A standard worth reaching when one is successful is roughly 120 chapters,for if one has 12 chapters per volume,that's 10 volumes.
Plenty of series,though,won't reach those heights,but 1/3 of it is when most artists/authors can cover an arc or two on a nicely paced ending.
There's also the obvious monsters who reach into 200+ and even 300+(some monsters even further),but end up either a large development that carefully eloborates on the whole thing or a drawn out mess that keeps having to come up with excuses for certain things(like rom-coms do).
So yeah,31 chapters is not short,unless the page density is half or less of the typical 20~ pages per chapter.