Over the past decades there were many, many attempts to make quartz metal halide arc tubes from UV-stop quartz. It does not work.
Firstly, the additives cause the softening temperature to be reduced. Arc tube loading has to be reduced to avoid premature failure, and that causes a decrease of the halide vapour pressures and inferior performance.
Secondly, the cerium-titanium and/or aluminium ions in the UV-stop quartz make it more susceptible to halide corrosion, so again reduced life.
Regarding the LED Filament G9 type lamps, quartz is required to prevent overheating of the silicone LED during sealing. That might sound counter-intuitive, since quartz has a much higher softening temperature than other glass types. But speed is of the essence here. With judicious use of liquid nitrogen coolants, quartz can be raised to its softening temperature, pinch-sealed, and cooled back down faster than normal glasses where prolonged annealing periods are required to remove stresses caused by the glassworking operation. It is really challenging with soft and hard glasses to cool them fast enough without cracking, and during that time there is greater heat flux from the glass to the LED inside, which can cause degradation of the silicone and thermal expansion related damage to the silver plated gold bonding wires of the LED chips.