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.
The 24-year-old has made five starts and scored one try for the Warriors since his debut in December.
Although Maitland's father was born in New Zealand, his uncle and grandparents hail from Scotland and he was brought up with strong Scottish roots.
"When I spoke to his Dad he was standing in his kilt in New Zealand," Johnson said. "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.
"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 RBS 6 Nations match at Twickenham on February 2.
Maitland has already starred at Twickenham, scoring two tries as part of the star-studded Crusaders side that beat the Sharks in a Super 15 match in March 2011.
Saracens flanker Kelly Brown, who attended the Six Nations launch with Johnson today as one of Scotland's senior group, said: "It's been really exciting to come into the squad and see all these young guys and new players.
"The guy I am really looking forward to seeing is Sean Maitland. He has some serious wheels. If we can give him some space, he could be really exciting."
Although Maitland will have fond memories of Twickenham, Scotland have not won there in 30 years - but Johnson dismissed 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.
And the former Wales and Australia coach cautioned against reading too much into Scotland's defeat to Tonga in November, which prompted the departure of Andy Robinson.
"Everyone focuses on the Tonga game but we did some good things against New Zealand and South Africa," Johnson said.
"We didn't get the result we wanted against Tonga and we have to acknowledge that but the reality is the world order has changed - these Polynesian sides are now quality rugby teams.
"The shock 'wow factor' about the loss to Tonga may no longer be the shock 'wow factor' that people think it is."
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.
"Despite what people think, we are going to turn up to this game. We aren't going to cancel it. We are coming. We are keen to go," Johnson said.
"There is an underlying will to ruin a party at Twickenham."
"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.
"But rest assured, come game time we may not be a poor little boy."