Sort of, not really? Most of BRK is invested in 100% wholly owned companies. They do have a "small"[0] public equity portfolio, that does change investments periodically, but most of those investments are also pretty long term, if you go look.

Wholly owned companies list: https://berkshirehathaway.com/subs/sublinks.html

0: In terms of BRK's overall wealth, it's still in the many billions of dollars.