From my little interaction with OSM community, I get the impression that any tag that theoretically applies to any form of transformation, will de facto skew toward cars. Cyclists and maps for cyclists just need to account for that, and place more emphasis on cycling specific tags. In this case, maybe it would help a bit if the bicycle-related evaluations were included in the table on the main page and not just in the gallery.
Agreed on your thoughts about how that terrain would be on a bicycle. Tires will mostly not sink, probably not even narrow road bike tires, it will just be extremely bumpy and unpredictable. Elevated chance of unrepairable sidewall damage to tires.
Any form of suspension makes it better (e.g. just a suspension stem/seatpost on a gravel bike, not necessarily proper mtb stuff), but it’s still going to be hard riding. Kind of similar to cobbles in that building up speed makes it easier to control, but that’s also dangerous as this surface is more unpredictable.