Phantom points in old games?

Recently I started going back and watching old NBA games to get a feel for how past stars played on a nightly basis instead of just watching highlights. I've been really impressed with the play of these old players, and I definitely understand the hype. But quite frequently now I've noticed something that I don't quite understand, but happens pretty often...

Basically I'll see a star player having a quiet night; a few layups here and a jumper there, maybe a couple free throws in between, but really nothing notable. We'll get to the 4th quarter and I'll be thinking "huh when is the star player gonna heat up?", but then the announcer will blurt out that said star player now has like 30 points. Most recently I was watching a game between the Celtics and Pistons from 1987, and it looked like Larry Bird was not playing very well; missing most of his shots and just hitting some open layups. Suddenly Bird gets to the free throw line and I hear the announcer say "Larry Bird now has 33 points going for his 34th with this free throw", and I was just completely lost. I had been watching intently for the whole game, and I didn't remember him hitting enough shots/free throws to even have 20 points, not to mention being even close to 34.

I've noticed this happen almost exclusively in games prior to 1990, and mostly by shooting guards or small forwards. Specifically Larry Bird (twice now), Clyde Drexler (couldn't even count at this point), and Julius Erving (at least 3 times) are the players I've seen it happen with the most if that helps. I don't know what it is about these players, but when I watch them they seem to fill the box score with points without making the amount of shots needed to get those points...

Has anyone else experienced this before, or have I completely lost my mind? Is there some explanation for why it feels like these players aren't scoring many points but the box score says they played amazing? If it was just one time I'd chalk it up to me not paying attention, but it's happened so often that it's gotta be something real.