Yes, I believe you are wrong.
I worked for a company that supplied test equipment and I visited the very small Naim production and sales facility at 11 Salt Lane many times during the 1970s for meetings with Julian Vereker. As late as 1977 all pcb and final assembly was being done by just a few operatives with no mechanisation. When they moved to the Southampton Road factory in 1980 they had just 9 employees. Here's a link to some interesting history:
https://www.naimaudio.com/our-story/18043/heritage
I was also fortunate to get a large file from a former Naim employee containing much useful technical, service and production information. I was given the file on the strict understanding that I would never put it in the public domain but I could use the information to help others on this forum.
I believe that the following document about serial numbers from the Naim web site is a little misleading:
https://www.naimaudio.com/serial-numbers
in that the serial number of 006933 given for 1982 represents the total production of the company from 1973/4 to the end of 1982 and is not the figure for 1982. Looking at the serial numbers for 1983 you will see that just over 5,000 units were made that year and this was a time of major growth for Naim.
In the very early days (1971 - 1973) very few units were made and many of these went to friends and relations, probably without serial numbers. The serial number information that I have shows sales of:
1974 - 54
1975 - 166
1976 - 426
1977 - 582
these figures are in line with the size of the operation I visited and indicate strong growth becoming limited by the size of the facility.
In recent years I've owned a NAP120 and three NAP160s and each one had date codes on the electrolytic capacitors that agree with the dates from the serial number information that I have. It's harder to date a NAC12 from its components but I've had three v3 12s with serial numbers between 08xx and 12xx. I know that one was manufactured in 1977 because I bought it from the original owner and the other two were very similar in terms of issue numbers on the daughter boards and the components used.