The current rules for stratification are built on the old formulas.
For example, suppose a club game has 12 pairs in a section, divided into four A pairs, four B pairs, and four C pairs. The first place A award is 12 * .10, or 1.20. The first place B award is less, for two reasons. First, there are only 8 pairs. Second, competing against just B players is not as difficult. So, the first-place B award is not .80, it is .64. That is a 20% reduction over what the A award would have been for the same number of table.
There are no principles to determine what this fractional reduction should be (at least that I know of). Instead, the only principle is common sense -- someone decided on a fractional reduction that seemed about right.
In the current formulas, the B players take an additional reduction (in terms of masterpoints per person) because 8 tables does not award as many masterpoints per person as 12 tables. The fractional reduction for B players was determined assuming this reduction for field size. When formulas are changed to eliminate the reduction for field size, this fractional reduction for B players presumably will be too low.
This principle is even more obvious for the C players. The C players of course have even fewer tables. And, they are competing against an even weaker field than the B players. Therefore, their fractional reduction should be greater than 20%. But it is not. This is illogical, except that the C players have an even bigger reduction for field size. When this reduction for field size is eliminated, the fraction reduction for the C players probably should be increased.