Are you observing the male catkins or the female structure? I ask because the pistillate flowers are tiny and unknown to most.

Anyway, if oak is too young, the female flowers won't fully form or the ovaries will abort fertilized eggs.

Sexually mature oaks will bear as only as many acorns as the tree can physiologically support and will abort the excess.

Interesting. There's lots of the male catkins.. I'll check for the female part