I have just found a couple of other APUG forum postings relating to the ektacolor dev replenisher concentrate bottle sizes in the 4*5L kits. It looks like, as I suspected, the concentrations were indeed changed at some point.

I thought I would add the references here in case anyone else finds them useful in the future...

http://www.apug.org/forums/archive/i.../t-105868.html
http://www.apug.org/forums/viewpost.php?p=1340557