Hi Johnny,
Question marks mean that the operation in that column is untested for this chip, untested on hardware. Usually it happens when chip definition is added based on datasheets information, but without testing on hw. Later if someone runs operations on the chip successfully, the chip can be marked as tested. Also sometimes chip definition is added and tested straight away.
This table on the website might not be fully up-to-date, and the best I would recommend is to look at the source , flashchips.c. This file contains all chip definitions and is fairly readable by the human eye (and you can search by chip name). If you need to look the source it in the browser for any reason, you can look in our github mirror: https://github.com/flashrom/flashrom/blob/master/flashchips.c
I just looked, and the question marks in your screenshot are still untested chips. Hope this helps.