Yes, doing optimizations on AST in CPython is unlikely to give any sizable speed improvements in real world programs. Python as a language is not suited for static optimization, and even if you manage to inline a function, there's still CPython's interpreted overhead and boxed types that dwarf the effect of the optimization.

The goal of this patch was never to significantly improve the speed. It was to replace the existing bytecode peephole pass with cleaner and simpler code, which also happens to produce slightly better results.