EDIT: I have wandered off my original point, which was simply that users of zoom and telephoto lenses also get an attractive size advantage from a smaller format; maybe even more so than use of prime of most focal lengths: my "not so much" means "less" not "none".
The 24-70mm is a zoom lens, which is part of the case I was talking about!We are talking slightly at cross-purposes here: I was talking about the size advantage that comes purely from a smaller format; you are confounding it with the further size advantage (in both bodies and some lenses) of mirrorless vs SLR, which I certainly do not deny! Further that 35mm is a wide angle for 35mm format and with the large back-focus distance required by the 35mm format EF mount, which adds to its size problem compared to a 25mm normal for 4/3" format with no mirror clearance problems.
A better comparison of what I am talking about would come from MFT vs Fujifilm X vs Sony A7 with FE mount lenses ... if there were enough of the last for useful comparisons!
Why not look at the size of the 35mm MF rangefinder lenses v all digital Mirrorless offerings?
You will see that the only way to get really small lenses is to make a smaller sensor (ie micro 4/3)
Or build a camera with a FF 35mm sensor and manual focus lenses, no in lens motors, no electronic aperture or OIS
The micro 4/3 lenses some of them are quite small and compact, but at a cost of sensor size.
If you want a bigger sensor, AF and in lens motors/IS in lenses you are not going to get small lenses.
This is the big problem for ILC makers, they can only offer somewhat smaller bodies v DSLR's, in the lens dept they can do very little (esp for APS-C and FF)