Yes good point. I thought about using H16, and then said no stick with H15 for the Rocket tutorial. I would strongly advise anyone else to do the same.
I see your point but…
A small recommendation from an old timer is that you should not focus on the specific “how to” guide of tutorials in general. But rather just learn the “philosophy” that they are using and translate that to your own tool, in this case Houdini.
Of course there are exceptions to this, but in general learning the “philosophy” rather than the procedure will help you a lot in being flexible for whenever the tool changes.