In many cases we'd say that buying older generation tech when newer models comes out is a good idea, as you can often pick up a great bargain, and you don't necessarily need the latest and greatest for many uses.
In the case of the iMac though, most people buying it will be creatives looking to render editing timelines and the like. As a result we recommend picking up a newer M3 chipset model than an older M1 variant, to help make this process more efficient.