BS
In the dialogue right before this he specifically mentions training Jedi for 800 years and how he had a council.
this one, a long time have I watched, all his life, as he looked away, to the future, the horizon
Could mean any one of his students in those 800 years, from Obi-Wan to Anakin himself. Before TLJ, you would never interrupt that he was watching Luke grow up. It was always meant to be interrupted as a student Yoda had that Luke relates to. Yoda even looks up to Ben as he says this and Ben is constantly reminding Yoda that he was once like Luke as well as a green, impatient youth.
And if I'm wrong and Yoda was somehow keeping tabs on him, then I'd chalk that up as is using foresight and sensing Luke's feelings in that moment, reading his heart and mind. In Empire Yoda IS watching him for a awhile before revealing himself. Luke tells him so much while in the guise of a crazy old creature. To think he projected himself at Lars Homestead and studied Luke is just absurd, and missing the point of the scene entirely. TLJ and ROS are a farce when it comes to time and space.
Lets not twist and warp the OT to fit the horrible sequels. I don't want Disney getting ideas of going back and tinkering with them even further after the damage sustained by the PT.