So paused charging for desktop mode at 80% on my new MacBook Air is a good thing?

Yes it is. See the following Apple Support article for information on optimized battery charging: If battery charging is paused or on hold on your Mac - Apple Support

including the following excerpt:

With macOS Big Sur or later, your Mac learns from your charging habits to improve the lifespan of your battery.

In macOS Big Sur or later, Optimized Battery Charging is designed to improve the lifespan of your battery and reduce the time your Mac spends fully charged. When the feature is enabled, your Mac will delay charging past 80% in certain situations. Your Mac learns your charging routine and aims to ensure that your Mac is fully charged when unplugged.

A feature introduced into Big Sur & Monterey and Ventura was to preserve the number of Full Battery Cycles.

There was an Algorithm coded into the macOS.

It is perfectly normal for Big Sur , Monterey, Ventura to Pause / Suspend charging the battery beyond 80% and hold it at that level.

One can nudge / over-ride this by clicking the Battery Icon on Desktop Top Bar and allow charging beyond 80%. From observations, it will Pause / Suspend again once reading 90%. Same procedure to over-ride and will charge to 100%

Gailster2 wrote:

So paused charging for desktop mode at 80% on my new MacBook Air is a good thing?

Yes. Please refer to the following Support Articles for additional information.

1. If your Mac battery won’t charge completely
2. If battery charging is paused or on hold on your Mac
3. Change Battery settings on a Mac laptop