At least I think this is talking about this as limitation/problem.
The limitation/problem being that it's not good/useful for performing after-transaction code only for specific actions.
But the next sentence "This is beneficial..." seems contradictory, so I'm a bit confused/unclear of what the intention is...
Looking at this project more, it doesn't appear to solve the "after-transaction code only for specific actions" problem like I initially thought it did (and like https://github.com/grosser/ar_after_transaction does), so I believe I was mistaken.
Still not sure what is meant by "instead of specific model actions". Are they claiming that "before_commit_on_create" for example is a "specific model action"? (hardly!) That seems almost identical to the (not specific enough) callbacks provided natively by Rails. Oh yeah, I guess they do point out that Rails 3 adds this functionality, so this gem is only needed for Rails 2.