Toast sesame seeds in a large nonstick skillet over medium-high heat until golden, about 3 minutes. Transfer sesame seeds to a small bowl.
Heat 1 tablespon oil in empty skillet over medium-high heat until just smoking. Pat pork dry with paper towels and season with salt and pepper. Cook tenderloins until browned on all sides, 5 to 8 minutes. Reduce heat to medium, add honey and 1/2 cup vinegar, and cook, turning tenderloins to coat, until mixture is syrupy and instant-read thermometer inserted in center of tenderloin registers 145 degrees, about 10 minutes. Transfer pork to cutting board, tent with foil, and let rest 5 minutes. Set skillet with honey mixture aside.
Combine cucumber, jalapeno, scallions, remaining 2 tablesppons oil, remaining 2 tablespoons vinegar, and 2 teaspoons sesame seeds in bowl. Adjust seasoning with salt and pepper.
Cut pork into 1/2-inch thick slices, transfer to platter, drizzle with reserved honey mixture and sprinkle with remaining sesame seeds. Serve with scallion salad.