Mary Shelley's novel would fit in with the mature SF of the '60s and '70s, but less so in the era of genre.
Is there any argument that all magic realism is liminal fantasy?
Seems reasonable to me, but I suspect Kazuo Ishiguro (for example) wouldn't agree.
Did Damien Walter ever follow up mentioning whether he'd found anything good?
Not that I'm aware. It's possible he was more interested in making a splash than actually getting wet.
Is there any argument that all magic realism is liminal fantasy?
Seems reasonable to me, but I suspect Kazuo Ishiguro (for example) wouldn't agree.
Did Damien Walter ever follow up mentioning whether he'd found anything good?
Not that I'm aware. It's possible he was more interested in making a splash than actually getting wet.