This sounds misinterpreted to me. He said can I buy it once and take it with me, which to me implies he wants to buy one copy and have his kids able to play it on theirs while he plays on his. There isn’t enough information in the quote to know what they are talking about. Taking that to be you can’t install it on two systems with the same account (even if that ends up being true) is a silly assumption.
That being said, it’s nintendo’s fault that these rumors happen because they tell us nothing.