A single season's hitting or pitching stats contain a vastly greater number of tests of the player's skill in those areas, than fielding. An outfielder has had a busy season if he collects 300+ total chances. Many of those chances are absolute cans o' corn. Conversely, and unfortunately, many other opportunities to excel (or to fail) are never recorded as total chances, and are recorded simply as "hits" for the opposing batter, even though the ball came into an area of the field where under other circumstances a play might have been successfully made. Other "hits" are truly unreachable by even the fastest player - the distinction is not noted in the traditional fielding stats. Analogously, a batter faces a certain percentage of pitches that essentially every batter would do the same on - 55-foot breaking pitches, fastballs that sail three feet outside, strikes taken on 3-0, and so forth. Those are like the cans o' corn, and/or the balls hit totally out of reach of a fielder. But a busy season at bat consists of nearly 3000 individual pitches; these chances to excel or fail get combined into hits and outs and eventually the slash-line. So when you slice and dice, "cans o' corn" versus more challenging plays (fielding and batting analogues to one another), there is 10 times the quantity of data to judge the hitter (or pitcher) on, than for fielding. (Shortstop is slightly less troublesome, with about 2X the total chances of center field.) We are accustomed to looking skeptically at Small Sample Sizes of batting stats - 100 PA may not tell you much about the player. More than 400 pitches might be involved in that. A season of defensive data is inherently SSS. Robbie Grossman may have suddenly gotten better in the outfield. Or, more likely, his 2019 has been the fielding equivalent of Hurricane Hazle (or our Danny Santana), hitting amazingly for a quarter of a season, until suddenly the pixie dust disappears.