They seem to be changing from their traditional one, originally designed for 600×800 pixel tablets

to

Presumably this is because modern avionics can display the latter well enough?
These two formats have been around since forever.
For the approach plate you got the small format that I print out on DIN A5 (it’s the actually the corresponding US format) and SIDs and STARs have the huge format that fits DIN A4.
No change that I can see.
Yep, has been like this for many years for certain charts such as departure/arrival charts or even taxi charts. In the printed version supplied by Jeppesen, the larger charts were printed on a larger sheet of paper and then folded back – not completely in half but with spacing so that the folded paper did not cover the punch holes.
Maybe it is my print process because the landscape plates used to print auto rotated to a landscape sheet 
Interesting you mention that, I just came accross this approach plate in LFRM… though it’s the first time I go there, don’t know if they were always this way, but it’s the first of its kind I see?

Never seen that before. What a massive waste of space on the page!! All that blank. I’m not confident that this is the best way of arranging the information. How do you see that georeferenced on the moving map? Everything to the east of the airfield is hidden (because the approach chart overlays it).
Indeed. It probably displays OK on a G1000 type of large display, if it is at least 1024px horizontally.
On an Ipad, you have to rotate it, somehow… It depends on the app used for PDF display and you have a choice. I’ve just tried it with whatever the default PDF app is (not sure how one can tell) and it does not auto-rotate, so you have to zoom-in manually, which is probably better. You can view the left half or the right half, of the plate posted above by roznet. No rotation involved.