I gave examples in the OP. For some OGL developers, they designated everything "Product Identity." Of 5E companies publishing under the 5.1 SRD released into CC, few are releasing their work into CC as well (to be clear, there is no legal requirement that they do so). Under ORC literally all mechanics in whatever you put under the license are Open. So companies like Kobold are releasing SRDs of their own, trimmed of whatever they want reserved, instead of releasing the actual game books under ORC as Paizo did (and I believe Chaosium did with the new BRP edition).