They're probably being forced into using email more because people will not all have the same free day so handing printed memo's and attached documents doesn't really work.
That does make sense and the only comparison I'm aware of would be a remote worker who you are just not going to start sending printed pages or faxes etc compared to digital forms, and in those case will often see closer to 100% reduction (alas some things need physical signatures).
I'm speaking from experience in UK/Sweden vs what I see in The Netherlands.
In some of the large organizations I've worked at it was the culture to distribute anything "official" - draft documents, meeting notes, presentations for meetings etc - in printed forms to a surprisingly large number of people.
Since I moved to mainland Europe - where a four-day working week is very much the norm for people with kids in high skill jobs - I have yet to encounter this practice.
Technology might also be playing a roll here, but large organizations have this tendency to fight any kind of change tooth and nail, it only seems to happen when it is forced.
