@Sabbamitta, your theory does not hold up to further inquiry, and Chinese texts interpret it the same way as the Pali counterparts:
Here are some Pali suttas that mention white-clothed lay Buddhists with less than 8 precepts - i.e. not celibate -, and their parallels (if any), to see if Chinese suttas also have laypersons who keep less than 8 precepts and still wear white.
MN 73 - Chinese parallels SA2 198 and SA 964
“Leaving aside Master Gotama, the monks, the nuns, the celibate laymen, and the laymen enjoying sensual pleasures, is there even a single laywoman disciple of Master Gotama—white-clothed and celibate—who, with the ending of the five lower fetters, is reborn spontaneously, to be extinguished there, not liable to return from that world?” “There are not just one hundred such celibate laywomen who are my disciples, Vaccha, or two or three or four or five hundred, but many more than that.”
“Leaving aside Master Gotama, the monks, the nuns, the celibate laymen, the laymen enjoying sensual pleasures, and the celibate laywomen, is there even a single laywoman disciple of Master Gotama—white-clothed, enjoying sensual pleasures, following instructions, and responding to advice—who has gone beyond doubt, got rid of indecision, and lives self-assured and independent of others regarding the Teacher’s instruction?” “There are not just one hundred such laywomen enjoying sensual pleasures who are my disciples, Vaccha, or two or three or four or five hundred, but many more than that.”
SA2 198 and SA 964 don’t mention “white-clothed”.
There is a partial Pali parallel to MN 73: DN 29 - The Chinese parallel DA 17 also doesn’t mention “white-clothed”.
AN 5.179 = MA 128
Then the Buddha said to Venerable Sāriputta: “You should know this, Sāriputta, about those white-clothed laypeople whose actions are restrained in the five precepts, and who get four blissful meditations in the present life belonging to the higher mind when they want, without trouble or difficulty. They may, if they wish, declare of themselves: ‘I’ve finished with rebirth in hell, the animal realm, and the ghost realm. I’ve finished with all places of loss, bad places, the underworld. I am a stream-enterer! I’m not liable to be reborn in the underworld, and am bound for awakening.’
尊者舍梨 子及眾坐已定，世尊告曰：「舍梨子！若汝知白 衣聖弟子善護行五法及得四增上心，現 法樂居，易不難得。舍梨子！汝當記別聖弟 子地獄盡，畜生、餓鬼及諸惡處亦盡，得須陀 洹，不墮惡法，定趣正覺，極受七有，天上人 間七往來已而得苦邊。
(No need to add a translation because it is quite similar to the Pali text.)
AN 5.196 - no Chinese parallel
White caterpillars with black heads crawled up from his feet and covered his knees. This was fulfilled when many white-clothed laypeople went for refuge to him for life. This was the third great dream that appeared to him while he was still not awakened.
So, there is at least one Chinese sutta, MA 128, that contradicts @Sabbamitta’s theory, and confirms that also in the Chinese texts, white clothes were worn by all kinds of lay Buddhists, whether celibate or not. I only had a look at Chinese parallels to Pali texts that matched my search criteria. It is quite possible that there are more Chinese suttas about this topic without Pali parallel, but I’m not going to search further.
Just as an interesting side fact, there are also white-clothed lay followers of non-Buddhist traditions:
Jains: MN 104, DN 29, DN 33
Naked ascetics: AN 6.57
Brahmins: DN 3
And there are plenty of references in the Pali suttas to people wearing white without being involved in any kind of spiritual or religious practise. So it seems that white clothes and celibacy had nothing to do with each other.