Possible Bug in Computing Surface Area of Certain Geometric Regions

Until this is fixed in a future version, here is a workaround for now:

Unprotect[RegionBoundary];
RegionBoundary /: Area @ RegionBoundary @ SphericalShell[c_, {ri_, r_}] :=
                  Area @ Sphere[c, r] + Area @ Sphere[c, ri];
RegionBoundary /: Area @ RegionBoundary @ CapsuleShape[{v1_, v2_}, r_] :=
                  2 π r (2 r + EuclideanDistance[v2, v1]);
Protect[RegionBoundary];

The idea is to add the definition to RegionBoundary instead of Area to avoid returning a wrong value if one applies Area directly to these 3D regions. So e.g. these

Area @ CapsuleShape[{{-1, 0, 0}, {1, 0, 0}}, 1];
Area @ SphericalShell[{0, 0, 0}, {3, 4}]

still correctly returns Infinity as they should; but with RegionBoundary we get:

Area @ RegionBoundary @ SphericalShell[{0, 0, 0}, {3, 4}]
Area @ RegionBoundary @ CapsuleShape[{{-1, 0, 0}, {1, 0, 0}}, 1]

$100\pi$

$8\pi$

as expected.