Some of the data is not available on Rice as it wasn't measured back then. It also seems there is a range of what Rice's 40 time actually was. We always hear about the 4.6 40 and it looks like the slowest recorded time was 4.71 while another watch had him at 4.45 so he was somewhere in the middle. Using the 4.71, he would only score a 4, but his hand size was just slightly under the average and considering the brick stories, his 9.5 hands were probably a lot more capable than many 9.5 hands. This is also being compared to the top 25 receivers from 2019 and also missing data, so he very well could be in the 5-6 or higher range with all of the data and if his real 40 was sub 4.5.
When I have time, I might compare him to WRs in his generation as he probably will grade out to the top, but compared to guys now he still grades out extremely high.