@Fizzie-DWG recently added static_tents=yes/no/number to tourism=camp_site.
Unlike with static_caravans, it allows a number in addition to yes or no to specify the number of static tents in a campsite. Either this option should be added to static_caravans or maybe new capacity:static_tents and capacity:static_caravans should be introduced. As capacity:tents and capacity:caravans are now defined as “number of pitches available”, this new capacity of static tents or caravans should be in addition to them, as they are presumably on pitches that are not available for your tent or caravan.
Thoughts? I have not looked at the 78 uses of static_tents=* in overpass.