That paragraph of the article looks to be ~6 years out of date according to the network manager version number it lists, around the time of the initial iwd release, and the whole article seems to be at least 2-3 years out of date since then iwd is well into version 2.x now.
Distros like Ubuntu have defaulted to iwd as the NM backend for Wi-Fi for a couple years (and now in the LTS version). It really is a quite popular and stable replacement to wpa_supplicant.
It looks like you're right [0], so I stand corrected.
It also looks like it can't fully replace wpa_supplicant though:
> IWD and the NM backend are work in progress and the capabilities are still limited.
[0] https://iwd.wiki.kernel.org/networkmanager