The need to confirm the instrument departure (SID) you will fly only arises with the HONILY and LISTO SIDs from 23L/23R.
Both the LISTO1R/1Y have restricted availability Quote (UK AIP): Available only to non-jet and the following jet aircraft: all aircraft up to 35,000Kg MTOW plus BAe146 (AvroRJ series); Embraer E135, E145: Bombardier CRJ1, CRJ2, CRJ7, CRJ9, BD-700 Global Express; Gulfstream 5. Everything else has to fly the HONILY1R/1Y
What has happpened in a very few occasions in the past, and probably once month even now, is that an aircraft not in the approved list has got airborne (usually having been given and read back a Honily with Delivery) and flown the LISTO. The issue is primarily one of noise, although it can throw up problems of speed difference especially when the jet you were expecting to do the round Knutsford tour on the HONILY turns left and starts eating up the slower turboprop or, even more entertaining, Navajo or Seneca on a LISTO
To try an prevent the inadvertant flying of the wrong SID, ATC is required to confirm with the pilot the clearance he has been given and the SID he will fly (Confidence Check) before the aircraft lines up on either 23L or 23R.
There is no need to confirm this on any SID other than the HONILY and LISTO from 23L/R. If you don't offer it when checking in with Tower on 118.625 (23R) or 119.4 (23L), we should ask.
Hope this helps to clarify another rather unique Manchester practice.