Maitland, who has represented the Maori All Blacks and the New Zealand Under-20s, arrived in Scotland in October after signing a three-year contract with Glasgow and, although Maitland's father was born in New Zealand, his uncle and grandparents hail from Scotland and he was brought up as "half Scottish".
Speaking at the Six Nations launch, Johnson said: "When I spoke to his dad he was standing in his kilt in New Zealand. Everyone thinks it's the grandfather rule that Sean comes under. Sean's father is Scottish and he has great pride in being a Scotsman. Sean used to be woken up as a kid to watch Scotland in the Five Nations, as it was."
He went on: "This kid is of proud Scottish heritage. This is not tokenism and he would be offended if anyone questioned that and so would his dad and his grandparents as well. He is a real proud Scotsman and he is there for the right reasons and that is why we value him as a member of this team."
Maitland will become the latest so-called "kilted Kiwi" if he makes his Scotland debut in their opening Six Nations match at Twickenham on February 2.
Scotland have not won there in 30 years but Johnson dismisses that history as irrelevant.
"That is news to me. A lot of these players probably haven't been there before. We have to create our own history and disregard what has occurred in the past," Johnson said.
Johnson is in the same interim position this year as Stuart Lancaster was with England last season and he is determined to use that to Scotland's benefit.
"The unknown factor is a good thing for us. We are the poor little boys on the block and we are happy to go in as the poor little boys on the block," Johnson said.
"But rest assured, come game time we may not be a poor little boy."
- Sports & Recreation