They don't say the scenario where that's happening, though. Unless your editor supports large file editing, a mode where it doesn't load the whole file into memory, unless it has filesize restrictions that make it just fail, if you throw a large enough file at it, it's invariably going to use a bunch of memory.

$ dd if=/dev/zero of=out.bin bs=1M count=500
500+0 records in
500+0 records out
524288000 bytes (524 MB, 500 MiB) copied, 0.100949 s, 5.2 GB/s
$ vim out.bin

On my system, after it (slowly) finishes opening that file, vim's using 511MB RSS. I know that vim has some sort of large file editing support, though not how to use it.

On emacs, large file editing support is from the vlf package.

$ emacs
M-x vlf RET
out.bin RET

Emacs is using 75.3 MB RSS after opening that.

Yes apparently. Apologies.