Yeah, basically. Pump heads held on by a rubber grommet have a lot of variability depending on the pump head, the condition of the gasket, and the tube stem. You push it on, flip the lever (or whatever), and if it leaks you redo it pushing in on further and trying again. If it still doesn't seal or stay on, put a new grommet in it and maybe then it will work. Some are better than others, but that's the basic drill. Thread-on types are much less temperamental and problematic. They thread over the threads at the tip of the stem and an o-ring seals against the shoulder at the end of those threads where the diameter of the stem increases (some have larger threads beyond the shoulder and some are smooth). Eventually that o-ring will wear out and need replacement too.

All these issues are just with the end of the pump head (chuck), everything before that usually works fine. So, chose a pump based on the pump head, or put a good chuck on the pump you have.