I don't agree, if what's coming out of the Piano and reaches your ears sounds good then it's pretty easy to record.
Not rocket science recording a good or excellent sound out of it
Then if the Player and the Instrument are both really good, or excellent, then there's no challenge whatsoever recording it,
it's pretty simple and even recording lesson 101 will achieve great results.
The challenge that is see in this scenario is screwing up, that would be pretty hard for a professional recording engineer.
This whole thing is quite massively off topic, but I find this opinion comes across just a little high and mighty.
Certainly if you have a good player playing solo, on a good instrument, in a good room, the job is drastically easier and the options become many. But in a live-sound situation, you may have one, two, or even three of those criteria being covered, but as Garp expressed (and was shown in the video), the amount of other instruments - and the volume of spill from horns and drums on the stage, as well as monitors bleeding into the mics creates a pretty huge challenge.
Some people might impulsively manage that situation well, but really, it's something that I think requires a lot of experience.
As for the Kölln Concert, I know that the story is there about the poorly tuned instrument, but I think we're still talking about a Steinway D - not exactly a piece of ****. Now, the reality that the whole recording was done with two U-67s and a 2-track machine (and then mastered with the addition of an EMT-140) probably drastically limited the total quality. I really enjoy many of the early ECM records, especially Martin Wieland's work, but I really don't think this is his best, even if it's his best-selling.
For me, in today's era of many mics on many tracks, it seems like an incredibly strange decision to have not brought an 8 track 1" machine along to get a few extra mics up and actually capture the sound of the piano in the hall. I would think that a couple of omnis in the room wouldn't have gone astray in there.
edit: I just read that apparently it was a Bösendorfer Baby Grand, so obviously not the same caliber of instrument. But I stand by the idea that having more mics could have potentially captured a larger (at least roomier) sound, but obviously without the bottom end of an Imperial. I played one once, and hot diggidy damn, that thing was insanely loud!
cDetailTopMoreOtherSeller,scm-url:1007.40050.354490.0,pvid:9e14b5c9-f7a3-4e53-9b9b-8eae125640d6,tpp_buckets:668#2846#8112#1997&pdp_npi=4@dis!EUR!2.63!2.63!!!20.11!20.11!@2103864c17224340303358059ed367!12000028436133406!rec!FR!165400745!XZ&utparam-url=scene
The mic had an ali K47 in it which was peaky in the middle and lacked bottom end as well as air. Now the mic sounds absolutely gorgeous, thank you 
