That may be true but your question was this:
"has anybody posted the before and after results of a transient response test?"
Maybe I should have been more specific. Has anybody posted any rigorous transient response test results?
There have been lots of posts showing fast edges from various sources but most are not fast enough and have questionable or unknown characteristics. That video is the only test I have seen with any credibility.
We know how the 'scope works internally so we know there's no physical difference between a DS1054Z and a DS1104Z.
The designs and production may be identical but Rigol could be grading them after production for the ones which will support 100 MHz with good transient response and the ones which will not. As I recall, the design includes no adjustments so alternatively maybe they do board rework which takes time adding to the cost.
Some modern DSOs apply frequency and phase compensation through DSP. The ones which can be field upgraded must have good transient response at their maximum upgraded bandwidth however Rigol does not do that so there is no such requirement for them.
While I have not seen it done at 100 MHz and I doubt Rigol did it, they could have relied on the stock passive probe to correct the transient response. There are some aftermarket probes with high frequency compensation adjustments which could correct it but of course this does nothing when a feedthrough termination is used. This is more common with higher bandwidth oscilloscopes.
The video shows a rise time on a hacked DS1054Z that indicates 150MHz bandwidth.
What more do you want? It's a $400 'scope...
It *is* a great deal but if the results shown in the video are accurate, then the hacked model may not be a 100 (or 150 MHz) oscilloscope in the same sense that that the genuine model is which is what everybody is claiming. An oscilloscope is a time domain instrument so I want the transient response to be as good as possible; if I saw the result shown in the video and it was accurate, then I would assume that the oscilloscope is broken or in need of calibration.
If I wanted just bandwidth, then I could tweak the high frequency compensation of on oscilloscope and get it at the expense of transient response. Tektronix actually did this as an option on their old 7704A which came in 200 and 250 MHz versions.
There is a guy on Ebay who takes 150 MHz Tektronix 2445Bs, bypasses the fixed bandwidth limiting filter between the delay line and vertical CRT amplifier, reconfigures them, and sells them as 400 MHz 2465Bs. Do they actually perform like real 2465Bs? They do unless the user looks closely and most users lack a 50ps reference level pulse generator which would reveal what is going on and they would not notice when using standard passive probes with their high circuit loading except under very controlled conditions. These hacked "2465Bs" have lower bandwidth and poorer transient response than real ones and can never be adjusted to meet the 2465B specifications.