The one that used the wrong phraseology initially was the controller. Not the pilot. It's understandable that the CX pilot sounds irritated.
1) He gets an RA, which means that the CTR controller had a deal (Controller's operational error).
2) Then the controller issues a "descend and maintain FL100". Transition Level for the US is FL180. Anything below that should be expressed as altitude not Flight Level.
3) Even when the controller corrected the mistake by saying "descend and maintain 10,000" she HAS to give the altimeter (ATC 7110.65 2-7-2.e
When issuing clearance to descend below the
lowest usable flight level, advise the pilot of the
altimeter setting of the weather reporting station
nearest the point the aircraft will descend below that
She didn't give the altimeter, which was her 3d mistake in a row with the same aircraft, and led the pilot to ask for the "QNH".
Probably she lost her nerve with the deal which is understandable.
As for the QNH, it is included in the PCG which is a requirement for the controller to know, thus it's included in the .65. The pilot was speaking English fluently. If the controller heard the word QNH for the first time in her life, what can I say...