That's the issue with the new push. Before, it was based on sales. If you downloaded the free version, you were saying that you weren't making enough money to consider it real income off of its use. If you sold enough, you could certainly buy the pro version with the sudden sales. However, if it's based on installations, and not sales, one user could install it multiple times on different computers using the same account, and installations of pirated copies could count if not properly cracked if they came from steam, etc. In order words, this only hurts the developers, as they are having their success measured in 'installations', not 'sales'. Also, while revenue is measured in the past year, installations are measured for the life of the game. In others words, they expect you to pay for each installation after the cap years down the line. And the best part is the cap: the highest plans have a cap of only a 1,000,000. You pay all that money for the better plans, only to cap at a million downloads before paying.
However, from steam's marketing perspective, I think the real goal of this is the push for upgrading one's unity plan. The amount you pay per copy is reduced the higher your plan is. Therefore, if you get enough downloads, it might be cheaper to pay for the higher plan each year to avoid the larger fee per download for life. So this is plainly being pushed to make them more money, which you would think they made enough, what with all the successful unity games out there.
There are workarounds, though. It only counts downloads from Unity-supported game platforms. It might call for a new game platform rises that refuses to count downloads. The chances of that, though, are slim.
