Heck, it hasn't been true since the 1950s. Consider it as "has never been true".

Oh, sure, there have been plenty of native-host-only compilers. It was never a property of all compilers, though. Most system brings-ups, from the mainframes of the 1960s through the minis of the 1970s to the micros and embeddeds of the 1980s and onwards have required cross compilers.

I think what he means is that a single-target toolchain is an anachronism. That's also not true, since even clang doesn't target everything under the sun in one binary. A toolchain needs far more than a compiler, for a start; it needs the headers and libraries and it needs a linker. To go from source to executable (or herd of dynamic shared objects) requires a whole lot more than installing the clang (or whatever front-end) binary and choosing a nifty target triple. Most builds of clang don't even support all the interesting target triples and you need to build it yourself, which require a lot more computer than I can afford.

Target triples are not even something limited to toolchains. I maintain software that gets cross-built to all kinds of targets all the time and that requires target triples for the same reasons compilers do. Target triples are just a basic tool of the trade if you deal with anything other than scripting the browser and they're a solved problem rediscovered every now and then by people who haven;t studied their history.