Just FYI a colleague was pointing out the same thing to me today (also with many digit numbers) but in the number col box.
Another oddity: the number col box (where it relates to a column at all, my example was the table made by Process Screening) uses only the overall preference for tables, it does not match a checkbox set just for that column.
@hogi What I see is that if I check Use Thousands Separator on a column that had started with width 12, it updates automatically to width 13. That will only give room for one separator on the largest numbers it could contain before. so bigger numbers don't show separator. Then if I change width to be much larger they can appear.
Also, are you in Switzerland? I was counting it as an amazing fun fact that this week in the process of all this about thousands separators I learned that there are places where you use ones other than . or , and that Switzerland uses apostrophe and then your example has that. I don't think I'd ever seen that before!