It certainly could also be trademarks, but I heard that in at least some cases it's because TF only covers the storage part of the spec, whereas the full "SD" s

It certainly could also be trademarks, but I heard that in at least some cases it's because TF only covers the storage part of the spec, whereas the full "SD" spec includes using it as an interface to non-storage stuff... although actually skimming https://en.wikipedia.org/wiki/SD_card#SDIO_cards https://en.wikipedia.org/wiki/SD_card#SDIO_cards now, I'm less convinced that that's a hard requirement in which case I'd agree that it's 100% trademarks instead of just 90%;)