SplinePhysics and BulletPhysics are independent physics solvers.

When first adopted in TP, Bullet only had standard rope behavior, and nothing really good for things like grass, trees, tentacles, galaxy arms, etc., so Cebas added a new solver that could evolve over time.

Spline Physics doesn't have object collisions, but you can use it with BulletPhysics to get collisions. However, Bullet doesn't have a "shape" interpretation for ropes (which is visible to TP), and Bullet only sees the knots for collision, so be sure to have enough knots in the rope.

You can fake a hull by using the Margin Value in SplinePool. Set it to half the hull thickness and the knot will collide properly.