ThinLTO, the scalable variant Google built for Chrome and that Clang ships today, exists because whole-program LTO's memory and link-time cost was too high for codebases with tens of thousands of translation units, yet the cross-file inlining win was too valuable to give up. The Linux kernel's Clang-based builds and Rust's release profiles both default LTO on for exactly the reason demonstrated here: a small function defined in one file can't be inlined into a caller in another file without seeing the whole program at once.