If you really think errors tells the whole story on defense, then you are right, there's no sense bringing this up again.
Here's what soxprospects has to say (not that they are the top scouting experts around):
Dalbec:
Field: Hands work well and footwork is usually reliable. A little stiff and has some trouble getting down on ground balls when charging the ball. Doesn't have great range, but makes up for that somewhat with his length, allowing him to cover more ground than his feet would normally allow. Has made great strides since he joined the Red Sox and now projects as an above-average defender at third base.
Arm: Plus-plus arm strength. Touched the mid-90s off the mound in college. Plenty of arm for third base, able to make all the throws including balls fielded on the foul line...has the potential to become an everyday regular at third base with good defense.
Plus, there is this to ponder... Red Sox Minor League Defensive Player of the Year (2018)
Chavis:
Field: Not the most fluid defender. Footwork is choppy and lets the ball play him at times. Hands work and has average range in the field. Has more range to his glove side than when going to his right. Has the raw tools to be at least a fringe-average defender. Started playing first base in the 2017 Arizona Fall League and second base during Spring Training 2019. Played shortstop initially after signing, but was moved off the position to third base very soon thereafter.
Arm: Above-average arm, able to make all the throws from third base, including deep against the foul line. Accuracy suffers at times due to sloppy footwork...Needs to make major strides defensively