But that's incorrect.

Super Armor doesn't qualify someone as " True Tank". However, being unable to combo a ninja does reduce the overall normality of damage someone would take.

Roshi is a tank. Scaling defense makes it so, and his core weakness is the early game. However, if he survives, his absurd survivability is shown. Topping it with Immunity to combat debuffs. He's a true tank.

Additionally, characters with scaling defensive stats (Defense, Res) are tanks. Jirobo, Kimimaro. Etc.

You can say the exact same thing about Roshi "Won't die in the right setups"