No, it's not technically a Silicon Studio IP. It's a Square Enix IP, outsourced to Silicon Studio. Just like Mario Tennis and Mario Golf are owned by Nintendo despite being developed by Camelot.
My argument is that they could have used this opportunity to create a Bravely Default spin-off and your counter-argument is "but it's not the same developer!" and "but they didn't". Why thanks for pointing out the obvious! It's pretty irrelevant whether Silicon Studio is developing a Bravely Default game or not, especially one that's a spin-off. Again, those are typically not developed by the team behind the main games in the first place. Bravely Default is based on Final Fantasy. Literally. It's the sequel to The 4 Heroes of Light (not developed by Silicon Studio, fyi). It has a lot of elements from Final Fantasy in it and I think they could easily have synced the naming conventions in Explorers with Bravely Default, call it Bravely Explorers and people would not have noticed a difference.
(And really, I didn't plan on just make comparisons with Nintendo games, but they're well know so they do make good examples).