In the early days of civil secondary-radar, when ATC had requested a flight to "squawk 2345," a common response once it had been selected was "...2345 coming down." The reliability and routine use of transponders later meant that, having acknowledged the new squawk, it was unnecessary for a crew to assure ATC that it was actually selected because they would soon tell you if it wasn't.
Hesitate to intrude into the conversation on R/T protocols because it's a long time since I retired but, in the 1980s and '90s, there were various efforts to try and eliminate the kind of R/T misunderstandings that - particularly when the reception of an ATC instruction was partially interrupted by transmission difficulties or being "stepped-on" - could lead to accidents like the one at Tenerife North in 1977. Thus "...line up and hold after the landing aircraft" was replaced by "...behind the landing Concorde line-up and wait," and the Dutch and Belgians would even add the word "behind" a second time at the end of the sentence.
They also addressed the ambiguity between the spoken words "to" and "two" in English. Thus "descend to seven zero", the sort of phrase commonly used by pilots in acknowledgment, was no longer acceptable, being replaced by "descend flight-level seven zero." For consistency, an instruction to climb or descend to an altitude would be delivered and acknowledged as, for example, "descend altitude five-thousand..."
Of course the U.S., as always, practises variations from ICAO protocols.