Unless the MAX to Rouge plan is completely scrapped. A321 won't be operated by Rouge in the future, there's nothing to be refurbished... (If I remember correctly, the cabin is very new, at least compared to XMs)

Also noting that 3 ex-EVA had already transferred from Rouge to Mainline, I wouldn't be surprised if more A321 is to be transferred to mainline.

Edit: I think the person on the other forum is suggesting that the A321 is there for decals/minor works in preparation for transferring to mainline while retaining the Rouge cabin. Which is also unsurprising if they do...