TBH I did not count the characters myself but used $len().
251 characters looks like one of these magic computer numbers. If you add the 3 dots, it sums up to 254 which is even closer to the whole byte.
It still does not explain why (locally) the same text sometimes gets displayed with 3 dots and sometimes it does not.
There was once this case of a docked window from another application that caused a miscalculation of window sizes
so perhaps something similar is the case here.