Here is a discourse from the Anguttara Nikaya (translated by Bhante Bhikkhu Bodhi) that explains how the word "Saṅgha" refers to more than just the community of monks.
AN 4.7 They Adorn
AN 4.7 They Adorn
“Bhikkhus, these
four kinds of persons who are competent, disciplined, self-confident, learned,
experts on the Dhamma, practicing in
accordance with the Dhamma, adorn the Saṅgha. What four?
(1) “A bhikkhu who
is competent, disciplined, self-confident, learned, an expert on the Dhamma,
practicing in accordance with the Dhamma, adorns the Saṅgha.
(2) A bhikkhuni who
is competent ...
(3) A male lay
follower who is competent ...
(4) A female lay
follower who is competent, disciplined, self-confident, learned, an expert on
the Dhamma, practicing in accordance with the Dhamma, adorns the Saṅgha.
Bhikkhus, these four
kinds of persons who are competent,
disciplined, self-confident, learned, upholders of the Dhamma,
practicing in accordance with the Dhamma, adorn the Saṅgha.”
One
who is competent and self-confident,
learned,
an expert on the Dhamma,
practicing
in accord with the Dhamma,
is
called an adornment of the Saṅgha.
A
bhikkhu accomplished in virtue,
a
learned bhikkhuni,
a
male lay follower endowed with faith,
a
female lay follower endowed with faith:
these
are the ones that adorn the Saṅgha;
these
are the Saṅgha’s adornments.
Note the phrasing of this discourse. The four kinds of persons are one thing and the Saṅgha is another thing. It seems that some persons, followers of the Buddha Dhamma, who are not so competent, not so disciplined and so forth, are still part of the Saṅgha though not 'adornments'. A person becomes an adornment through greater alignment with the Dhamma. The more a person lives in accordance with the Dhamma, the more the Dhamma shines forth and the greater is their capacity to adorn the Saṅgha.