The usual scenario for these type of incidents is that ATC make a mistake, which the flightcrew don't realise and struggle to comply with, possibly due to poor handling skills, resulting in a dangerous outcome.

In this case, the flight crew were challenged with a last-minute ATC instruction, which was perhaps unexpected but to them quite reasonable, they correctly read back, and the ATC had an opportunity to correct but didn't. The flight crew then successfully executed the requested approach, but also initiated go around when they saw a traffic conflict.

It is quite fanciful to think that if the single word "confirm" had replaced the word "understand" the whole thing wouldn't have happened. I really can't see what the crew did wrong here, it seems they are being blamed for being TOO competent.

I think we can go back to the "holes in the cheese lining up" accident model proposed by Prof. Jim Reason ..... The BEA report identifies 4 big holes in this particular cheese (and a few smaller ones....): none of them big, jagged, sudden holes, but big enough to let a nasty smell though if they had lined up - 3 ATC holes, and 1 Pilot hole. Which, by multiple decent situational awarenesses, enough decisive participants, a big sky, and a happy dose of luck, they didn't. Long may that last.

donotdespisethesnake

We are not in the business of apportioning blames and in this particular case nobody did a "mistake". A slip of the tongue ( lapsus) is per definition inconscient , You mean to say something but your brains says another and you do not realize it . It happens during periods of high mental workload, and happens quite often in our professions , although most of the times without consequences as it is corrected by the person seating besides you , the PF if you are flying your coordinator/ assistant if you are a controller. The first " hole" in this incident is that she was alone to take up Gary Brown remark about Reason's model. .
The UAL crew did not do any "mistake" either they performed what was asked as it is common to do so in the USA and they used the FAA phraseology they are most used to.. the other hole here.
Another hole was that the sophisticated automated conflict detection tool in the TWR supposed to detect such things did not activate ( reasons explained in the BEA report)
However 3 holes were closed and that is why it was only an incident :
The EZY crew by looking out if approach was free while lining up closed a hole, it was good airmanship.
The UAL crew spotted the attempted line up and performed a go around even before it was mentioned on the R.T another hole closed
The visibility allowed visual detection of the conflict.

Gary Brown : Indeed, most probably one of the reason that caused her lapsus.

When I flew for Continental Airlines we were operationally required to be stabilized by 1000' agl. Staggered runway threshold distances add an additional destabilizing element . A side step request by ATC below that altitude would elicit a simple "unable".

UPDATE Sept 2nd 2021 - English version of BEA Final Report just published:

https://bea.aero/en/investigation-re...-de-gaulle-ad/

I transited French airspace twice yesterday.

Not a single controller listened to any read back or corrected the three incorrect read backs we heard, not a single controller listened to our initial contact messages containing info like where we were direct to, what our cruise level request was etc. One called us easyxxx twice before we managed to convince him we were from a different company and there was plenty of French only chat.

They only transmit, they don’t listen to what comes before or after. It seems to be policy because almost all of them do it.

Curious comments , you have to be a bit more specific as to where and when it was and was was unsafe in your eyes. . In Cruise in Upper airspace the controller anywhere does not have to read back anything. If it is extremely busy he/she will only acknowledge the call, not the contents.
As to not picking up the incorrect read backs, it is definitively not a policy anywhere, but as some of us have Mode S downlink of your aircraft parameters, and those are more relevant , a bad habit of not concentrating on R/T readbacks but what you actually see selected in the FD might be starting here. Not good. Lastly one comment you made would indicate a call sign confusion, yes. that is still a real and serious issue. and valid for everyone, pilots too....