Robinson featured prominently in the opening three rounds in Australia, Dubai and South Africa after being given a chance to perform on the international stage by John, who was impressed by what he saw in the rising talent.
"He performed really well for us over the first three rounds of the Seven series," explained John. "He's an exciting young talent. He is very quick, agile and strong in the tackle. When he was away with us he was keen to learn. It's great to see youngsters getting an opportunity."
When announcing his selection, Gatland compared the former Wales Under 16, U18 and U20 wing to his namesake, ex-England star Jason Robinson.
"He reminds me of Jason Robinson in the way he darts around. He has been very impressive in Sevens, which has been an avenue for a few of our players, and he has come on for the Blues and looked sharp.
"He plays with confidence, he is young and we need to be thinking in terms of the back three, which has been an area where we have not had a huge amount of strength over the last couple of seasons. We are looking not just to the immediate future, but at seeing how he will be over next two or three seasons."
Robinson isn't unique among the newcomers in the extended Welsh training squad to have come from Sevens.
Ospreys scrum half Rhys Webb spent three productive years with the Sevens, culminating in the stunning World Cup triumph while his regional teammate Ashley Beck played in tournaments in South Africa and Dubai in 2010.
Wales Sevens manager Dai Jenkins predicts bright futures for all of his protégés, particularly Webb.
"Rhys won't be a flash in the pan as he did the hard yards with us over three years," said Jenkins. "Sevens is a fierce testing ground for the players. They have to play six games in two days. Rhys was with us from 2008 - he came through from beginning to end with flying colours. He has the ability to go all the way with Wales."