It depends on what sort of panel has been used. You can get 1920x1080 as 22" monitor, but also as a 55" TV... Eizo for sure has/had 19" 1600x1200 models (e.g. FlexScan L771).

Also, technically LCD screens have a single native resolution (not a set of real displayable resolutions like a CRT), and everything below that is just an interpolated mess (which sometimes looks OK, if you have a really good screen from Eizo or NEC etc. with top-notch scaling units). And 1280x1024 is 5:4, not 4:3. Your Philips is therefore most likely a 5:4 model if it reports 1280x1024 as its "maximum" resolution (i.e. native resolution).

There are common native/max resolutions found in specific screen sizes but yes, they can vary.
For example you can expect a mainstream 17" to go up to 1280x1024, but this doesn't mean there wasn't some (like your benq) only reaching 1024x768.

It also depends on the age of the monitor, as LCD tech improved and the ability to create smaller pixels became more readily available. For example, a 17in LCD monitor made around 2005 might be able to support 1280x1024 or 1280x960, whereas a 17in LCD monitor from 2000 might only support 1024x768. Cost is also an issue. A lower-cost, more generic brand often will not support the same resolution as an equally-sized name-brand monitor of the same age.

There are some 20" ones that do 1600x1200, like the Dell 2007fp/fpb. I have one, it's great.

Eizo has a 26.5" 1920x1920 display - EV2730Q-BK. Not really 4:3 but a nice square screen.
You could "abuse" it as a letter-boxed 1920x1440 display. Although a bigger 2560x1440 one might only cost half as much while displaying the same canvas pillar-boxed.
As mentioned before - there are some nice 20"ers around e.g. HP's LP2065 which is cheap while featuring a high quality picture(1600x1200 S-IPS).