Dating a watch: movement serial or manufacture date?

1958 is my birthyear and I love to collect watches of this year (if not too expensive of course).
About dating, nearly all the omega serial numbers tables available on the net date 1958 movements between 16 and 17 millions. Years ago Desmond Guilfoyle from Australia (a well known omega collector) told me that 16 million serials were produced from 1958 to 1961, and if I wanted to be sure of the movement having been manufactured during 1958, I should go for the earlier 16 millions, in any case under 16.6 millions. Some time ago I found a nice Omega slimline (14451) in white gold, 540 movement, with a 16.2 millions serial and I bought it. When the omega archives extract arrived I was surprised to find that watch was manufactured in january 1961. What are your opinions about it? I would suppose that they actually manufactured the movement in 1958 but assembled a watch with it only in 1961, so I still consider it somehow from my birthyear. A few weeks after mine, I was able to find another exemplaire of the same watch, this time in rose gold, and I bought it for my wife. The serial is still 16.2 millions and only 124 numbers difference from mine! For this I didn't request the archive extract so I don't know when it was actually manufactured.
A few pics:

I'm also a 1958 baby. After trial and error I just decided to go with the movement's estimated manufacture year rather than the extract, because of the extract date difference. You'll drive yourself nuts trying to get lucky on both matching.

I agree with efauser, I have seen pics of archives extracts with 16 million serials going from 1958 to 1961, and I don't believe it took over 3 years for them to make 1 million of movements. One of these has 16.02 millions and is from 8/58 and mine with 16.22 millions is from 1/61. So over 2 years and a half to make 200,000 pieces? I don't think so. Moreover there are numbers within these two dates without any logical sequence, for example:
- 15.98 12/58
- 16.02 8/58
- 16.22 1/61 (mine)
- 16.27 10/58
- 16.80 4/59
- 17.50 7/60
As I don't think they manufactured movements with serials going backward and forward, they probably produced the movements in years close to what we find in the tables, but put them in the watches whenever they needed, without caring of the year of manufacture. So I will continue to think that my slimline is still from my birthyear 😀