That second one is specifically an N95 mask plus a surgical mask. The one I linked did just the N95 alone and then also the N95 + surgical mask on top of that.

The evidence suggests that placement of an SM on one type of FFR improved inhaled breathing gas concentrations over the FFR without SM; the placement of an SM over an FFR+EV probably will prevent the EV from opening, regardless of activity intensity; and, at lower levels of energy expenditure, EVs in FFR do not open either with or without an SM.

They even specially mention this in the results section. And in the conclusions saying

"The differences in inhaled gas concentrations in FFR+Surgical Mask and FFR-only were significant. The orientation of the SM on the FFR may have a significant effect on the inhaled breathing quality and breathing resistance, although the measurable inhalation and exhalation pressures caused by SM over FFR for healthcare users probably will be imperceptible at lower activity levels."