To achieve 1280x1024 in one of my older monitors I had to use interlaced mode and a 43.5Hz refresh rate. Remember: we're talking interlaced in here.
If you mean that the default RR was 60hz for most monitors I would agree [even though it's a responsability of the OS], but you said it was the average, not the default. For it to be the average, someone would have to use less, hence my 43hz reference.
They used to be a pretty common way to get to higher resolutions without buying a new monitor, but then again, it was really yucky.
Here are some common video modes available when monitors weren't so powerful, note specially the ones marked as 'interlaced'.