I asked on my old S:NGP-spin-off forum, where he has hung out since near time immemorial:
https://paleface.net/z/monkey/barrel/65237.html
He said:
I think I heard something about this once but have forgotten it - I think the idea was that people knew about game ROMS and this had more “rom space” and so the “rom rom” made it seem bigger? But I’m not really sure! I know that I don’t like it, ha ha.
And the other PC Engine experty person there said
When a Japanese boy named Ramu is small they will call him Ramuramu…I think that’s it. It’s to make it seem cuter.