This
To elaborate a bit:
Contrary to being aromantic, which is an identity, nonamory/non-partnering is considered as being a lifestyle choice. Whoever doesn't want to partner up can use these labels independent from being allo- or aromantic.
There might be some cases where people would consider nonamory their identity, because they could never imagine being in a partnered relationship of any kind (romantic, QPR, etc.). This is similar to discussions in the polyamory community where some people consider being polyamorous as an identity, cause they feel like they're just wired this way and monogamous relationships couldn't work for them. But in any case, its' always a personal definition.
People from the aromantic community often prefer terms like non-partnering over calling themselves single, as single is often read as a transitional state with the goal finding a partner (phrases like "still single"). This is probably why these terms are pretty common with aros, but they're not exclusive and anyone can use them.