Yes, it's important to take into account the energy efficiency of water electrolysis from non-renewable electricity, which is of course lower than in the case of methane reforming. That is why I do not recommend water electrolysis using non-renewable electricity.
Conversely, when 100% renewable electricity is used, the environmental footprint is very low because, regardless of efficiency, the electricity is renewable, meaning, it is available and merely needs to be captured. Whatever the efficiency of a wind turbine, a hydroelectric station, solar panels or an electrolyzer—which, might I add, is now nearly 65%—the energy is 100% renewable.