What a stupid phrase ! Sqwarking indicates 'transmitting' and standby indicates 'not transmitting' so what they are really telling you is to "transmit not transmit". Whats wrong with 'turn off your transponder'???
Squawk Standby - 3 syllables, easy to understand and quick to say, especially as it's normally given in conjunction with "contact tower (freq)"
Turn off your transponder - 6 syllables and a real gob full when given with the contact tower part of the message. The idea of R/T useage is brevity, not who can transmit the longest sentence possible.
You'll be saying we should adopt that bloody ridiculous Americanism "Taxy into position and hold next!" (How many runway incursions did that cause when the good ol' CAA termed Holding points as 'positions' for a short while - enough said!
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CM