Though Jango was not there is a missing part of Boba's history between the clone wars and the OT. And if it gets a chance I hope the show addresses this time. Was he a foundling or was he like Jango and an imposter? I would think that the Mando would have known of Fett so would have recognized the armor when he saw it, and going by his reaction it seems to me that he became a Mandalorian. I could be wrong.