So just by way of background, used to be That bottom brackets were an integrated system with the spindle that cranks attached to and the bearings that allowed the cranks to turn all part of the bottom bracket system. Older BBs are three pieces, with separate cups and spindles that are assembled in the bike’s BB shell. Newer but still outdated cartridge BBs have the spindle and cartridge bearings all together and are inserted into the frame as a unit. Then the early 2000s happened and the bike industry discovered they could increase crank stiffness and decrease weight by pulling the spindle out of the BB and attach it to the crank. So BBs became just bearings that are in various ways, depending on type, inserted into the frame. Ultegra cranks that work with this latter type of BB will have a spindle attached to the drive side crank arm that slides through the BB. The non drive side arm attaches to the end of the spindle on the other side and is tightened with two pinch bolts. If you have this type of crankset, your BB didn’t snap, your crankset broke.
This. And they'd replace the BB (cheapest part of the system) because you're already in there.