After he was gone, they realized just how beneficial his ability to purify the toxins out of the meat and other foods was. They have had much more difficulty with eating for many dungeons, and they also have lost enough companions to realize how precious those comrades are. As such, having one seemingly returned from the dead to them would be an extremely emotional experience for multiple reasons. As such, I thought it made sense.
According to me that old man can possibly see 3 things
1. He will see nothing
2. He will see some glitched numbers/words
3. He will see soo many weaknesses that he will think mc is useless