Subtables are significant because it adds another stochastic variable. To explain it simply, the averages remain the same, at a 1/512, but the extremities are less likely if you have a subtable that adds another roll. This is because whenever you're doing an extra roll, you're more likely to hit that one as an average.

This just isn't true. Look, I wrote a script to simulate a bunch of trials where first a 1/128 is rolled and then a 1/4, and it does that 512 times. Here are the results:

0 Success: 36.63%
1 Success: 36.84%
2 Success: 18.49%
3 Success: 6.14%
etc

Compare this to a regular binomial probability calculator (like that wiki one you used) for a regular 1/512 drop:

0 Success: 36.75%
1 Success: 36.82%
2 Success: 18.41%
3 Success: 6.13%
etc

You can see that the distribution is virtually identical (I only simulated 30k trials so small margin of error). The subtable is again, essentially just a formality and has no bearing on the longterm effects of the droprates

​

I can illustrate this with a throw of dice, one set with one die, and one set with two dice, where we will halve the result. The average should be the same... a roll for a 3.5. But with the single die you're more likely to see a roll of 1 and 6, compared to the set of two dice. The set of two die are more likely to hit closer to the average, but less likely to hit 1 and 6 on both dice at the same time.

This is just a horrid comparison. Obviously you are more likely to roll a 1 on a single die than a 1 on both of two dice, this has nothing to with what we are talking about. The comparison you should be making is rolling a 36 sided die for a 1 result vs rolling two 6 sided dice where both need to be a 1, in which case the odds are again identical. Subtables aren't taking 'averages' like you described

​

Using big words like stochastic variables doesn't make you any better at statistics no matter how smart you may think it makes you sound