I don't think that's the case about it being pride. It's pretty common for intelligent people to immediately forget minutiae. The fact that folk completely forget work over the weekend means they're fresh for a new week. Throw taking care of small children into the mix, and there's zero room for anything extra rattling around.
"I don't remember what I did yesterday," seems more likely to really mean, "there's nothing that anyone cares about." It's an answer to the question that they wanted to be asked, i.e. "What does the team need to know about the progress of your work?" Framed in response to what they were actually asked, "what did you do yesterday?"
It's actually a pretty good response, assuming they're generally effective employees. They are avoiding wasting everyone's time conveying what they believe to be unnecessary information.
You can run a more effective startup by directly asking for status updates on important tickets rather than vaguely asking, "what did you do?" Ask for information, not a story. If you literally want folk to go into minutiae on something because you think it would be helpful, then ask them for that. "How did you solve that problem?" And they'll ramble on the whole meeting.