Well, you may be able to save money by keeping it in or under your mattress, but I can think of many ways that are better in the long run. If banks are charging people to keep their money and only paying 1/100 of 1% interest, then what's the big deal about putting money in off shore banks?
If it's out of their home country, and they have all the benefits of living in that home country with that amount of money, but none of the taxes that their home country would levy on that money, (as the article we're discussing says) then YES, that is obviously the case. They are avoiding taxes.
The onus is on the claim maker, and if you read the links you are supporting you should know the answer, or as it appears to be the case are simply putting forth an assertion unproven or perhaps totally false. gossip: Casual or unconstrained conversation or reports about other people, typically involving details that are not confirmed as being true.