There's some confusion on the facts.
1. The "so-called 'mayday' transcript" (post #17): I first saw this Monday afternoon on avherald). That person called it "Some transcript of the EHRD Approach ATC". Now it's come here as the "Discrete Emergency Frequency". I have seen no indication that this transcription is authentic, especially because what we do have is from EHAM tower up to the point that the controller instructs to tune to "126.675, the Discrete Frequency" (and not "right frequency" as the Youtube transcription has it). 126.675 won't show up on your plates, but the scanner crowd calls it the "Arrival BackUp / Discrete Frequency", as distinct from 120.875, the "Discrete Emergency Frequency", which is what this transcript is claiming to be. In any case, it ain't Rotterdam Approach. Also, the Captain shows a distinct preference for communicating anything half-complicated in Dutch. Finally, whatever they may have said, it looks like once the controller realized that the flight was low on fuel, having control problems, AND was unable to change frequencies, he treated it as an emergency, even if the flight crew didn't want to declare it.
As far as I know, there are three possible sources for such a transcript: A. The official ATC tapes, which have not been made available, nor which would likely have been leaked. To be honest, I wouldn't expect those tasked with making a transcription would be required to come in on a weekend to do it. B. The CVR, likewise. C. Other listeners on frequency.
In category C there's anyone in the area with €15 Euro USB dongle, but also two websites: ATCBOX and LiveATC. ATCBOX has practically all Schiphol frequencies (including 126.675, as well as 120.825 ), but does not (as far as I know) archive them, so someone would have to be listening to/tuning to them in real time. This being the internet, there are some who claim to have been doing exactly that, and to have heard no such calls. LiveAtc has archives - indeed, it is the source of the traffic posted on youtube and on ED.nl -, but it does not archive 126.675 at Schiphol.
So it's been posted under dodgy circumstances, with patently false attributions, and no clear path back to any reliable source. Unless someone tells me where it comes from and how it was made, I'm calling fake.
2. As stated, Eindhoven does not accept alternates, only emergencies. Transavia operates most of their flights out of Amsterdam, Rotterdam and Eindhoven (with maybe a couple flights from Maastricht and Groningen), so the interest not to go to Brussels or Weeze (where other LoCos run, but not Transavia), or further afield.
3. The Dutch weather service issues a Summer Storm Warning once every five years or so. This was the worst such storm on record. It's not usual weather for the region, so plan accordingly.