New (2023) MacBook Air with Apple M2 chip support for external monitors?

No. Although it's worth noting it could drive two monitors if apple didn’t limit it via software.

The spec is confusing as it follows the one external monitor clause with Thunderbolt3 and Displayport2 support which both show capacity for multi monitor.

You can also buy a displaylink adaptor (~£70) and download 3rd party software to get it to work.

OR Apple could not artificially limit their own products, and mis-advertise specs like Displayport (lack of MST has been a long running issue).

The Displaylink isn't a standard dock. From this guide:

Many multi-display docks use a combination of native USB-C Alternate Mode (native “Alt Mode” video output) and DisplayLink technology. This combination serves as a workaround to the M1/M2 platform supporting only a single external display via USB-C.

It's a software/hardware workaround that does a fine job. That article also points out at one point Apple had agreed to fix the problem. Until then the OP may want to consider this workaround or request the feature using Apple - Feedback to ask that their products, all of which are premium in the general computing space, carry standard features found on most mid range laptops from the past decade.

No. It's basically the same as the 13" M2 MacBook Air, except that it has a larger screen, has two more speakers, and weighs more. So the limit of one external display still applies.

No: MacBook Air 13- and 15-inch with M2 - Tech Specs - Apple

Docks don’t increase the number of displays supported. Use of a dock provides the ability to attach more displays but the Mac's software and OS do not support the use of multiple external displays and the display performance (resolution/speed/quality) will be deteriorated to the point of being unsatisfactory/unusable.

RE: "That article also points out at one point Apple had agreed to fix the problem."

That article is misleading. If you follow the link to the other MacWorld article – the one that supposedly describes this "apparent promise' – you will find that it says no such thing.

The linked MacWorld article said that with M1-based Macs, "far from all resolutions are available for connected screens" … and then said that Apple had promised to fix that. Not that Apple promised to increase the number of monitors.

https://www.macworld.com/article/675911/apple-promises-to-fix-external-monitor-problems-with-m1-macs.html