Gary, anybody who followed that advice would be taking an extremely dangerous course of action in my view.
The recipient of the Notice of Intended Prosecution has a legal obligation to inform the Chief Constable of the identity of the driver of the vehicle at the appropriate time.
To ignore the letters would, and WILL, render the individual liable to prosecution for an offence under Section 172 of the Road Traffic Act 1988 pursuant to which a Summons would be issued, the offence being failure to notify.
The penalty for which is a hefty fine AND 6 points on the license.
If THAT Summons is ignored, it will result in the individual being arrested and remanded in custody following the issue of a Bench Arrest Warrant by somebody like me, or they would be tried in their absence, receiving notice of penalty points and fine through the post (and let's not contemplate where THAT will lead us).
I deal with these cases day in and day out and the number of times I've heard "I never got the documents" you just wouldn't believe. A bit of a non-starter as a defence because there are usually two Notices sent out plus a very strongly worded Final Reminder.
As a guideline, the average fine we hand down for this offence would be in the region of Â£500 assuming the defendant is employed and on an example income of Â£400 per week and an immediate guilty plea. It is considered way more serious than a speeding offence, tantamount to attempting to pervert the course of justice.
In view of the above, perhaps you might like to post (diplomatic) challenge, along with an explanation as above for example.
It might make you persona non grata with some though, as they'll probably work out where you got the information from
BTW, you weren't the only person to raise this