The only NIP I have ever gotten (err, so far....) was certainly dated and the keyword with NIPs is "issue". That means "popped it in the mail", it does not mean that you get it within 14 days. So one should always allow at least 21 days before you considering oneself clear of the last lapse in concentration with regards speed.
As to the whole "demanding names before the offence"...think it through. The police think that some vehicle was doing something iffy. Let's say driving without due care, just for the sake of argument. So they look up the keeper and punt them a letter asking "Were you driving XZY 123 on dd/mm/yy?"
I do not believe you have admitted to any offence at this point if you say it was you. That comes when you get the "Right, you nawty boy/girl..." paperwork.
If not, they punt the paperwork off to whomever you claim the driver was.
Upshot? YOU do not get to know about what proceedings are being taken against SOMEONE ELSE. Just like when any other crime is committed. The police don't knock on the door and say "Were you walking home along Some Street at 0400? Only someone committed XYZ against ABC, y'see". No, first they try to figure out who the hell the suspects might be and the suspects get to find out. You only get to know if it hits the press. After all, the allegations could be unfounded.
Of course, I may be being unduly naive in trying to see through the anti-police, "Oh woe is us!" spin MCN puts on just about every story.