I believe ThermionicScott is correct that a more expensive bottom bracket would not sell well along with an inexpensive crank.

However, the UN26's plastic non-drive side cup works well and is only broken by improper installation and removal. To install it properly, install the cartridge unit firmly first, then install the plastic cup loosely, torque the cartridge to spec and finally tighten the plastic cup snugly but no to anywhere near the full torque a metal cup specifies. To remove the bb, remove the cartridge side first, then the plastic side will come out by hand. Done right these plastic cups are creak free and last as long as the bb.