I have been discussing just this case with Richard from Seaward.
The thinking when this facility was first added is that the polarity on a multi-way extension block is only lkely to be wrong at the plug end. This is because the inards of the extension blocks are pre formed on manufacture.
I have a case where I would want to test, as you do, a multi socket end of cable. I also wanted this test to do earth1, insulation 1 polarity 1, then earth 2, insulation 2, polarity 2 etc.
Currently the tests do all the earth tests, then all the insulation then the one polarity. This means you have to move the connection twice through!!
I even submitted a psudo code to show what I was thinking.
The last I heard was that the firmware for the Europa Plus has been settled for some time now, and it is unlkely to be modified again in the near future. I even have three or four other suggestions of enhancements to the firmware. The more others, the merrier and perhaps Seaward might go for a revision!!