Yep. That's reality. HAMB is only as effective as the player makes it. It really doesn't take hitting a million balls anyway. If you hit a thousand balls every day for about 3 years, which would take around 5 hours per day, you'll have hit a million balls, and though you might be better than you were when you started, there's no guarantee you'll become a great player.
It's all about the quality of practice. If you pay attention during these 5-hour practice sessions, learning from mistakes, building fundamentals, etc... it would take only a few weeks to become a fairly strong and consistent player. And that's playing everyday, or at least 3 or 4 days per week.
The vast majority of players might hit a thousand balls every weekend in game situations, missing quite a few shots, not really practicing or pushing their brain to higher levels. As this pace it would take nearly 20 years to hit a million balls, and though you'd likely be better than you were when you started, you would not be a consistent/great player. You would improve much quicker by hitting a hundred balls per day, really focusing on the process and results. It takes less than 1 hour to hit 100 quality practice shots. Within a few weeks you'd be hitting em pretty strong, and that'd be a fraction of hitting a million balls. So it's not about quantity....it's about quality.