It will appear as a primary contact which under DS rules, need to take 5 miles laterally
Well, not quite. MATS Part 1 advises:
In the event of clutter being present on the situational display controllers should consider the nature and extent of the clutter and if necessary take the following actions:
a) For aircraft in receipt of a Deconfliction Service, controllers should inform the pilot of the extent of the clutter and where practicable offer a reroute. However, this may not be possible due to traffic density, airspace availability and/or the requirement to follow specific arrival or departure tracks. The extent of such a reroute should where possible aim to achieve the planned lateral deconfliction minima from the observed clutter. However, it may still be necessary to reduce traffic information/deconfliction advice from the direction of the clutter as detailed at Section 1 Chapter 11.
Note the "if necessary", "where practicable" and "where possible".
NS