As mentioned here already, crews often (incorrectly) squawk ident wihout being asked.
We need to readback the squawk ident instruction so that the ATCO can confirm that the correct aircraft has done so - instances of aircraft squawking within being asked or taking instructions intended for others are abound, as I'm sure we recognise.
If an aircraft is required to ident at all, it is because the ATCO wishes to identify an aircraft
unambiguously - they can't do that without a readback.
Hence CAP413, regardless of what we were 'taught'.
I think 'ident you have' is lazy phraseology, but I don't think it's the end of civilisation!
Now "ready on reaching", that's another story.....
