That's not the case - the 32gb config in these machines is regular DDR4, not Low-Power DDR4 as the lower-spec ones. This possibility was already there two years ago. Apparently they just ship a bigger battery to compensate for higher power requirements - something that was suggested when the 2016 model came out (and promptly dismissed by the Apple faithful as wishful thinking).

Intel only shipped their first LPDDR4 big-ram chips last May [1], and they are not the type Apple would use (not powerful enough). It's possible that Apple decided to go ahead with this configuration as a temporary solution, and will eventually swap-in "real" LPDDR4 chips when they land.

[1] https://arstechnica.com/gadgets/2018/05/intel-makes-its-firs...