It might be that the originator of the letter is a member of one or both sites hence the expertise.
The German findings are based on what has been built so far plus what is being passed to them direct from Amati in the previews.
If you read Sergio's response it he mentions the provision of the preview issue #51, this is way in advance of this mag hitting the streets in Germany as there build is only at issue 42.
This also answers the previous query of how many mags in front of the actual build Amati/Hachette have in hand, seems to be 9 or 10
So, I presume the Germans are simply basing there findings on what has been supplied to date plus the preview mags, even so this only gives then up to 51 but maybe enough to genearte the letter, so one might ask what other errors might we to discover, at 51 it just over a third of the way in to completion.
It seems that someone in Germany is carefully comparing the Hachete build against a Bismarck plan of some description, though this plan may not be quite the same as the plan that Amati have.
Who is right or wrong will come to light but all the same there are most definately problems such as the location of the Anchor, this is clearly wrong, as for the portholes etc etc then someone in Germany seems to be well clued up on how it should be, or it could be that they have got it very wrong due to having wrong plans?
Surely Amati and the German guy cant both be right
The highlighted Anchor error is such an obvious error on Amati's part, it makes you wonder what else have they got wrong.
It could well be that the German guy has hit the mark in what he says and at the moment it does appear he is very close to the truth, if so then both Amati & Hachette had better invest in some serious head gear as tin hats wont save them from the fallout