Here's an inside scoop: there's more to player analysis than height and vertical jump
I never said there was not. I professed a preference for certain traits.
Anthropometry is the scientific study of the measurements and proportions of the human body. Tests of anthropometry include measurements of body size, structure, and composition. There is a wide range of ideal body shapes and compositions, depending on the sports, the playing position and the fitness level. Tall players usually come with large hands and a long reach too.
There are reasons, teams measure these traits. This is why they say prototypical tight end or this or that. Is it the end all, nope and players can do well outside the norm. But Grant isn't one of those guys given his metric and athletic ability so far.
The G league is filled with prototype NBA bodies. P
Thank you for making my point, the minor league of professional sports is full of those guys. So is the NBA. This ought to tell you something that this body type does well at basketball. The YMCA is full of guys who are not and so are the majority of guys who never play past grade school. Are there guys outside it that do well, yep. But it is beyond ridicule to pretend that Grant is doing well with his stats.
If your going to draft a 6'5" PF like Grant Williams. He better be special in other areas. Grant Williams had a 32 inch vertical at combine. 32 inches. That is pathetic.
Even worse his standing vertical was 26" which is below NBA average. This is the kind of jumping on jumpers, to block shots and rebound where you don't always get a running leap.
Standing Vertical Leap – 26.0 inches
https://www.rockytopinsider.com/2019/05/20/how-vol-players-performed-at-2019-nba-draft-combine/Agree well said, the mix of below average vertical and size is not optimal.
The average NBA standing vertical leap is 28" (71 cm).
https://www.topendsports.com/testing/results/vertical-jump.htmSo as said above, not is he short for his position but his leaping is well below average for the positions. His wingspan is greater than this body by 3" and his standing reach is nothing great at 8'8.5" for his height but not good for his position.
You could end up missing on a Charles Barkley, Calvin Murphy, Isaiah Thomas, Marc Gasol, Nikola Jokic, PJ Tucker, Ben Wallace, etc.
Not really, in fact, here are some pics.

Charles Barkley has broad shoulder, narrow wast than shoulders, longer than torso legs check.

Isaiah Thomas has broad shoulder, narrow wast than shoulders, longer than torso , even thought he is shorter check
https://s.hdnux.com/photos/01/07/76/35/18868037/3/rawImage.jpg
PJ Tucker has broad shoulder, narrow wast than shoulders, longer than torso
The V shaped body with longer legs and shorter torso is the NBA prototype. This is true of Ben Wallace too, look at pictures folks.
So guys can be muscular and this type. But longer legs is longer levers for leaping and longer limbs for various aspects of sports like reach and wingspan. I never said a guy had to be tall to be this type. as Gouki88 insinuates, what I am saying this there are biomechanical advantages to this body type for run and jump sports. Just as short limbed guys can lift easier on certain lifts.
They take these measurements at the combine for a reason folks. They can cause guys to rise and fall in stock in the draft. How many times have we heard T-rex arms etc. There are guys outside this norm that succeed. But there are far more guys who do succeed with this body type than Pear shaped guys with large backsides which is what the OP was about.