How do vendors assign a cut grade for fancy cuts?

[sunshowers]

I’m browsing diamonds online, as you do when you are isolating at home during a pandemic, and am wondering how on earth vendors sort fancy cuts into the various cut grades. It seems so wildly inconsistent, what’s the point?

For example, this oval labeled ideal looks horrendous to me: https://www.jamesallen.com/loose-diamonds/oval-cut/1.00-carat-g-color-vs1-clarity-sku-8233000

Bonus question... what kind of oval cut is this? It showed up in my search for ovals: https://www.jamesallen.com/loose-diamonds/oval-cut/1.01-carat-g-color-vs1-clarity-sku-7703584

 

[tyty333]

Pretty sure its done by the numbers. No one views the stones and says "Hey, this looks like a really nice stone. I'll give it a cut grade of Excellent".

Second stone you posted...I've got no idea what the cut type is. Doesn't look to fall within any of the typical oval cuts I know of.
You'd have to request the GIA report and look at the pavilion diagram to see what it is (or isnt).

These are the main/traditional cuts I know of.
4 main
6 main
8 main
8 main offset
10 main

 

[Garry H (Cut Nut)]

Mostly by depth and table % which is like a dart board that is 2 metres away and 5M wide center target

 

[headlight]

For fancy cuts you really need to go with what is attractive to your eye. It’s what is called shape appeal. When it comes to fancy cuts, all bets are off with regard to proportions. If you want to think of it in a proportions context to a round brilliant, think of it as someone who prefers a small table and higher crown versus someone who likes a more spready stone with larger table. It’s what appeals to your eye. Fancy shapes are cut based on what the shape of the rough dictates to get the best yield. Rough that is more desirably shaped octahedrally is used to fashion round brilliants; other shaped rough is used for fancy cuts, generally speaking.
The first option is horrible. I am intrigued by the cut of the second and you should request to see the report as I’m curious as to what they identified it as to cutting style.
I have seen websites where they just assign their own definition of what’s excellent.