I wonder if it's what an ILS approach is called has something to do with it.At our UK unit we call it an ILS approach.However overseas I heard it called an ILS/DME .The R/T used there was ''Cleared ILS/DME approach''.Perhaps if they hear that phraseology used,then copy an ATIS that says RWY23R ILS DME is u/s,then they could misunderstand that the ILS ,and it's procedure was not available.(perhaps
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However we inform the aircraft on first contact what type of approach they can expect.If they had briefed for an alternative approach,then why not carry on with that,as long as the wx is within limits.