Well, I think the article may be right (I have not seen not read the article!). What you stated as the increase in volume leads to decrease in pressure (Boyle's law) is valid in an enclosure and this may also be true for an idealised adiabatic air parcel in the atmosphere. But for the general open atmosphere, the total atmospheric pressure is the sum of the dry air pressure and the pressure of water vapor (that should be Dalton's law), so if the vapor condenses into liquid water then the vapor content has been reduced leading to reduction in atmospheric gaseous volume and also reduction in the pressure contribution from the water vapor! The overall effect is the reduction in the total atmospheric pressure.

Yes it is true. What you are observing is the vapour pressure. When some of the vapour condenses there is less vapour so the vapour density decreases as does the vapour pressure, although the total mass and density remains the same.

Hi

The answers of Mr. Oladiran Johnson Abimbola and Mr. Alastair Bain McDonald are fair enough.