I haven't yet seen anybody pushing for "short functions" literally that didn't want a hardline on the largest function you should create. Thus, I haven't seen anybody explicitly using it as an heuristic instead of a rule.

People have all kind of heuristics that correlate with short functions, like DRY and single responsibility principle. People do apply those as heuristics. But function length is a number, and it is very hard to keep your conclusions fuzzy when operating over numbers.