The 10 perceptions in the sutta are meant to be meditated upon? Aniccasaññā is then not to be understood as empirical seeing the 3 characteristics, but contemplating on impermanence, right?
In the Girimananda Sutta, there are nine perceptions (sanna) preliminary to the development of direct seeing of Anapanasati.
The explanatory Pali word is 'paṭisañcikkhati', which means 'to think over', as follows:
Idhānanda bhikkhu araññagato vā rukkhamūlagato vā suññāgāragato vā iti paṭisaṃcikkhati:
There is the case where a monk — having gone to the wilderness, to the shade of a tree, or to an empty building — reflects thus: 'Form is inconstant, feeling is inconstant, perception is inconstant, fabrications are inconstant, consciousness is inconstant.' Thus he remains focused on inconstancy with regard to the five clinging-aggregates. This, Ananda, is called the perception of inconstancy.
to think over, to discriminate, consider, reflect
Also used in MN 19 and AN 3.38:
As I abided thus, diligent, ardent and resolute, a thought of sensual desire arose in me. I understood thus: ‘This thought of sensual desire has arisen in me. This leads to my own affliction, to others’ affliction, and to the affliction of both; it obstructs wisdom, causes difficulties, and leads away from Nibbāna.’ When I considered (paṭisañcikkhato): ‘This leads to my own affliction,’ it subsided in me; when I considered (paṭisañcikkhato): ‘This leads to others’ affliction,’ it subsided in me; when I considered (paṭisañcikkhato): ‘This leads to the affliction of both,’ it subsided in me; when I considered (paṭisañcikkhato): ‘This obstructs wisdom, causes difficulties, and leads away from Nibbāna,’ it subsided in me. Whenever a thought of sensual desire arose in me, I abandoned it, removed it, did away with it.
'Now I too am subject to old age and am not exempt from old age. Such being the case, if I were to feel repelled, humiliate and disgusted when seeing another who is old, that would not be proper for me.’ When I reflected (paṭisañcikkhato) thus, my intoxication with youth was completely abandoned
Similar to 'paṭisaṅkhā yoniso':
Paṭisaṅkhā yoniso piṇḍapātaṃ paṭisevati
Reflecting properly, they make use of almsfood:‘Not for fun, indulgence, adornment, or decoration, but only to continue and sustain this body, avoid harm, and support spiritual practice. So that I will put an end to old discomfort and not give rise to new discomfort, and so that I will keep on living blamelessly and at ease.’