Why can’t TTG’s Allowable Changes result in manipulations carried to extremes?

Because all of TTG’s Allowable Changes are reined in by rinairs in P7 of the Trust Test.

In other words, if any of TTG’s Allowable Changes were carried to an untrustworthy extreme, the result wouldn’t meet P7 of the Trust Test and thus wouldn’t qualify as TTG.

What about manipulations not allowed by TTG?

Since rinairs does not allow manipulations that TTG doesn’t allow—

—there is nothing (in P7 or elsewhere) to keep photographers from carrying non-TTG-allowed manipulations to extremes.

In other words, there is no non-arbitrary way to set limits on non-TTG-allowed manipulations.