Yeah, she'd been taking care of him for possibly a few cycles of de-aging and I guess at that point the age difference was too evident to say she was his mother directly and instead chose to pose as his Grandma. Who knows, if it looped again pretty recently, which it probably did considering he said he didn't recall his old school, he may never have known she wasn't... Quite sad honestly...
Someone commented a few chapters ago that this seemed like this would make them sad, and I disregarded that comment, thinking this was sure to end happy. I'm now, like the characters, incredibly uncertain of the future. 🫨