I think it would need an angled pocket, because it's supposed to be a replacement for the GIbson wrap-around bridge, like the Gotoh 510. The Gotoh needs an angled pocket, therefore the Baby Grand would too.
If you're using a trem, Fender, WIlkinson etc., or a Fender American Standard or similar fixed bridge, they are not as tall as the wrap-around style, so therefore no angled pocket.
If I'm wrong, then I will defer to someone with more experience.
A call to Warmoth, or an email to them or Hipshot should answer this easily.