Ok, so I searched the forums and found an answer all the way back from 2013:
My VRC motor memory tells me to accept @Karthik’s word as the final, but for the sake of the argument I must resist. 
@wdr_mentor I understand your argument about longer non-threaded section.
I did more research and found 2" brand name screw at $50/100, that has really long non-threaded section: https://www.mscdirect.com/product/details/70222443
In their value collection, MSCDirect sells 2" screws for as low as $26/100 but none of those have similarly long non-threaded section. Apparently, you have to pay premium for the rarely used parts.
However, if I expand my search to 2.5" screws, I could find a screw in the value collection with non-threaded section similar to the premium screw but at an affordable price of $26/100: https://www.mscdirect.com/product/details/85326924
If I cut that screw to 2" legal length limit, it will be functionally identical to the brand name screw, but at about half the price.
My understanding of RECF/VRC mission is that its goals include making the program affordable and accessible to the wide student audience to maximize the outreach of the STEM education, and also to provide fair and level competition environment for all kids.
It is important that everybody plays by the same rules, but wouldn’t it make sense to write and interpret the rules in a way that makes more resources accessible to more teams and not only to those who could afford to pay premium prices for the exquisite COTS hardware?