Unfortunately he's talking rubbish.
Insurance contracts are based on the principle of 'uberrima fides' or utmost good faith. So if they ask you have you got any points/convictions etc etc in the last 5 years and you say no on the basis that you've had them removed from your licence after 4, then you'd potentially be paying for a worthless piece of paper with some details on it - they could void your policy for non-disclosure of a material fact. Whether they will or not, is another matter, but not one I'd like to find out after having an accident.
The question over having to disclose them after 7 is a subtly different one. Due to s4(1) and s4(3)(a) Rehabilitation of Offenders Act 1974:
Originally Posted by s4(1)s5 deals with the periods for rehabilitation, but broadly for any fine or other sentence subject to rehabilitation (that isn't otherwise identified in the Act) is five years, and so after that point, no one can compel you to disclose the conviction due to s4 above.Originally Posted by s4(3)(a)