Yes, this is typical for games, particularly older ones or ones based on older game engines. There is one thread that acts as the core of the game and directs other parts of the CPU to do less critical tasks that can be done in parallel. Everything else has to stay together to function, so it must run on a single core in a single thread. It may move that task from CPU core to CPU core to prevent local overheating, but it can still only do one thing at time. Which is why single thread performance has always been important to games, still is, and why when AMD finally caught up and surpassed Intel with the Ryzen 3000 and 5000 series we finally had competition again.
Also related to why I stopped overclocking. Typical boost profiles will allow one or two cores to run a little faster than an all core overclock (in my case, 5.2 Ghz) with no action on my part. All core overclock of more than 4 cores is mostly just inefficient.
This is why the first dual cores were such a huge change back in the day. Your game ran on one core by itself, and Windows and all its tasks could be relegated to the other. Compared to single core systems this was a huge gain even if the CPUs weren't twice as fast (they typically were, and then some)
We've moved on from quad cores and hyperthreading is now basically standard in all but the cheapest CPUs.
Now the big move is towards lots of cache, the fastest memory type available to improve general CPU core performance.