These events have no evidence that they hold to the probability listed and cannot be verified.
The data is there, it does support the veracity of the RNG. . You just missed it, it's not easy to see.
Any given Event a lot of players post their Feedback. Some are unhappy they didn't get what they wanted, others talk about the riches they garnered.
Exactly what should happen if there is a random element.
Much like collecting significant data on one aspect, the data is there, it just takes years of reading the forums.
Which is why you'll rarely see long term frequent posters unhappy with the RNG.
Let's join a devs meeting in progress.
Dev 1: I got an idea, instead of using an RNG, let's use a pseudo RNG table. We can weight it so that at the start the results are below average so folk will spend Diamonds to get more attempts.
Dev 2: How do we beta test that?
Dev 3: Wouldn't more players give up because they are losing too much at the start?
Dev 4: Doesn't that mean we have to track where each player is on the pseudo RNG table? More data and more traffic and more server load?
Dev 5: Seems like it may cost us some amount to program, test, deploy?
Dev 6: What happens if players figure out the pattern? Remember what happened years back to the OL Poker games that were using crappy RNGs?
Dev Boss: So we can stay with the RNG and avoid pissing off players who will quit early on, save money on server load and internet traffic and data space and programming, and not risk ruining our nearly two decades of game building reputation?
Dev boss: Dev 1 you're fired.
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A fundamental of programming, KISS, (or if you prefer a rule of life, Occam's Razor) applies here.
INNO doesn't need to spend more money using a pseudo RNG table.
They've demonstrated they know how to extract money from their customers by using means that do not upset their customers.
What is not possible to collect are the other short term events that time out or close due to completion.
Regarding your original complaint?
You can collect a lot of data personally.
Start a new city and do Aztec Settlement (don't complete! just build a lot of Goods buildings) until you've collected a few thousand productions. Log each one with percentage and payoff. Then find a statistician to review your results and draw any conclusions. If INNO is using a pseudo RNG table it will be obvious.
Takes time, sure. That's on you, you're the one trying to grind an axe here.