I was able to get the Intel® Turbo Boost Technology box checked with an Intel® Core i3 processor. However, after saving the changes and restarting the option remains disabled. So, even though we can probably agree it looks like a bug, it is merely cosmetic because the option does not remain enabled (or saved) since the processor does not support it.
The memory voltage indeed remains close to the 1.5v value because the memory controller in the processor supports this voltage with a tolerance of plus/minus five percent. Other low power processors support 1.35 volts such as U/Y lines of products.
Desktop 4th Generation Intel® Core™ Processor Family: Datasheet, Vol. 1