It is noticeable.


If this person has previously made deposits of large sums in centralised exchanges, he/she will not have any problems, because he/she will have already filled in enough paperwork.

The problem would be someone who has somehow kept bitcoins out of the sight of banks and authorities and suddenly turns up with millions of bitcoins from who knows how. But if it's someone who has a lot of millions, either they won't have done it that way, or they'll have ways of bringing it to the surface via alleged profits of companies or something like that.