Wiktionary has attestations for use of 'blind' to mean 'concealed' or 'not visible' going all the way back to the 16th century, and if you follow the etymology it becomes likely that that was the original sense of the word, with 'sightless' coming later. This same disingenuous reasoning was used with Twitch with the phrase 'blind playthrough' (to mean 'playing a game without having seen any of it before').