Why is this stone an ''excellent'' cut (per GIA)?

[rocking80s]

Perhaps I don't know how cut grades are assessed, but it seems (and I was told by the jeweler I am talking to) that GIA certs are frequently wrong (so, don't put too much weight on them). The following diamond was pointed out as an example:

Report Type: GIA Diamond Grading Report

#16782987
Round Brilliant
Measurements: 6.48 - 6.52 x 3.90 mm
Carat Weight: 1.01
Color Grade: I
Clarity Grade: SI1
Cut Grade: Excellent
Proportions:
Depth: 60.0 %
Table: 60 %
Crown Angle: 33.5
Crown Height: 13.5 %
Pavilion Angle: 41°
Pavilion Depth: 43.5 %
Star length: 50 %
Lower Half: 80 %
Girdle: Medium to Slightly Thick, Faceted
Culet: None

Finish:
Polish: Excellent
Symmetry: Excellent
Fluorescence: None

To me, it seems the depth/table do not really seem to be very ideal. Am I (or my jeweler) missing something? I've been putting A LOT of
emphasis on AGS/GIA certifiations (of course, followed by my own inspection)... are they misleading at times (as in the case above)?

Thanks!
-r80s

 

[strmrdr]

Its a traditional 60-60 and would likely get an AGS0 rating from AGS if the numbers within the averages were good.

The traditional 60-60 has a different look than the ideal cuts of today but are very pretty stones and when well cut deserve the excellent rating.

 

[strmrdr]

Here is what the HCA says about it:
Selected: 60% depth, 60% table, 33.5° crown angle, 41° pavilion angle
The result is for a symmetrical diamond with a medium girdle and very good polish
HCA scores were adjusted Dec. 15, 2001 and Feb. 6, 2003.


Factor Grade
Light Return Excellent
Fire Very Good
Scintillation Very Good
Spread
or diameter for weight Excellent

Total Visual Performance 1.7 - Excellent
within TIC range

 

[lisa1.01fvs1]

The table seems rather large but perhaps the rest of the proportions compensate.

My stone is the exact wt. (1.01) as yours but table is 57% (6.43-6.46-3.99).

Don''t know what my AGS scores would be.

 

[strmrdr]

Here is a virtual aset with perfect symmetry that shows what such a combo at its best can look like under the ASET.