[Update - 12/26/2025] - Taiwanese outlet, CNA, has received a statement from ASUS regarding the DRAM rumor and stated that it currently has no plans to invest in a memory wafer fab.
https://wccftech.com/asus-enter-dram-market-next-year-to-tackle-memory-shortages-rumor/
If they made DIMMs with CXMT chips, they wouldn’t need a fab (CXMT presumably has access to those). ASUS already has the PCB production and pick-and-place factories.