Whilst all in favour of clear, concise and helpful R/T the problem comes when reported height information is based solely on SSR Mode C. I think the verified/unverified part is a red herring - the following applies whether verified of not.
As many above may have already said, the Controller is using a display where all Mode C information is converted to the same pressure setting(s). It is therefore deemed better for the Controller to relay relative height information than the observed height readout.
For example: Let's assume you're in receipt of RIS, decending through 2800' to 2000' on an QNH of 983mbs. The controller has unknown traffic indicating 3000' on the display. This height readout has been corrected to the SAS so is actually reading 900' high (1013-983 = 30. 30x30=900). If you were told the a/c was at 3000' you might be fooled into thinking "I'm below that and descending, it isn't a factor", whereas in truth you're still descending towards the other traffic.
To avoid this situation therefore, the Controller should compare your SSR height read-out (that has also been converted) with that of the other a/c and only pass relative height information i.e. "indicating 700' below you". True there will be a minor time-lag due to SSR data-transmission/display update rates/RT time - but ISTM that is still safer than giving a completely false impression?