Isn't what we are experiencing here just by definition random?
If a set of 3 items are selected randomly at any one time you will see more of one or less of one than the others, but the longer you conduct the test for, the more those levels even out.
I've seen this constantly with events, different people being short of different items at different times. í ½í¸‚
So for Virtual Adventurer having logged this for years the results are pretty even. For the simple test I'm currently helping Charlie with our levels are evening out the further into the test we go.
Yes, there are other factors to take into account, but me and Charlie are at different levels, different barn sizes, different amounts of coins, cash and materials. I'm still building zoo enclosures and expanding land...but our results are pretty much the same.
To be honest I'm not sure Playrix needs to rig things so we spend more money, people's impatience will get them to spend enough anyway.