'The testing distance is not silly, but shooting a plane target at this distance is silly'
Edward's post above nails this, in my view. I would choose an appropiate lens for copy art if that was my interest. The problem is the planar form of the target, how it misrepresents lens performance in 'image space', and the role of curvature.
It's a classic example of measuring procedure efficiency leading and distorting results presentation. I see this all the time in statistical data series evaluation - users will not read the methodology notes and and factor them in - they just want the results so they can draw long bows with them!
An example - the markets get excited because the US employment rate drops...why does it drop? The participation rate falls as more people get so discouraged they stop looking for work. Changes in the PR are the biggest influence on UE but the media and markets are blind to it, and just report the 'headline rate' of UE.
And data always looks convincing - just as with PZ bar charts, with resolution measured to four digits.
'It seems that the ZF improved noticeably on wide open and edge performance at a cost of some CA.'
Yes, I knew this and the background as to why, but I don't mention as many people here use the later vsn - which is also wonderful, and is in keeping with modern Zeiss lenses being better wide open. But it's one big reason I was happy to buy the original.
I would quibble a little with the 'better edges' meme. At 18mm IH (f5.6), the ZF lines are all way apart, at the maximum separation in the chart, and this separation continues until the extreme point of coverage of 21.5mm. It's especially obvious for the critical 40 lpmm - think fine structures, like twigs against a bright sky.
The ZF sagittal does very well in value terms, then plummets (much like the 25/2) whereas the tangential is smoother, at a lower level - leading to differential imaging as a result, quite likely, of CA. In the image centre the CY is also stronger (at f4-5.6). It can be expected to yield more consistent, accurate imaging with a steadier decrease, centre to corner.
This parallelism of MTF lines is best seen in the recent Distagon white paper, where Zeiss publish MTF at f4 for the CY version - the 40 lpmm lines (sag and tan) are identical in value and show ~83% at 5mm image height; I have never seen higher in real world infinity MTF testing, there may be one or two around. Certainly nothing in the current ZE/F range, nor the G range, nor the CY range.