It's definitely a gaia thing. I'm sure it's found elsewhere in the sort of amateur art world (using the term amateur only to differentiate from the gallery academic/fine artists, etc).
I've always seen the term "semi-realistic" applied to stylized art that is realistically shaded rather than simply colored.
This artist pair exemplifies this style because of the beautiful lighting scheme on top of a stylized anatomy.
Realism in the academic setting is not like those
portraits you see of Jack Sparrow, which are heavily influenced by or that reference photography.
Classical Realism is about skill and craftsmanship, light, value, anatomy in the classical/Old Master tradition.
Realism is a modern movement that puts the ordinary person up on the pedestal, so to speak, and has strong socialist undertones.
I would differentiate "semi-realism" at least in the sense it is used on Gaia, from
fantasy art, because most fantasy (Boris Vallejo, Frank Frazetta, Michael Whelan, etc..) tend to be more starkly realistic (anatomically, etc), where semi-realism tends to have stylized proportions but beautiful light and value.
Not to say that they aren't all equally incredible. :3 Anyway, that's my perspective.