It’s a silly flag to use as it only works when running 32-bit Windows applications on 64-bit Windows, and if you’re compiling from source, you should also have the option to just build a 64-bit binary in the first place. It made a degree of sense years ago when people actually used 32-bit Windows sometimes (which was usually just down to OEMs installing the wrong version on prebuilt PCs could have supported 64-bit) if you really wanted to only have one binary or you consumed a precompiled third party library and had to match its architecture.
It’s been the default since 2015 when Windows 10 launched, although there was an obvious button to opt out during first-time setup back then which was then respected permanently. It’s got gradually less prominent over time, and maybe the article’s just doing a really bad job of explaining that it’s no longer something where your initial preference is permanent and it’ll change back to the default every so often.