Linked video is still a great talk. Carmack comes off as someone who could talk about anything for a literal fortnight, so the 'mmm' may've been a tick where he was forcing himself to shutup & let the interview continue
It's not like people go home and talk to their partners about vertex shaders for a half hour.
Granted I've watched every QuakeCon keynote that was posted and enjoyed them all (along with reading every .plan). His enthusiasm is infectious. Yet even then he is breaking it down to the big things that happened that year, not the day-to-day stuff.
If it were over the dinner table every night, I'd probably lose my mind.