Preheat grill to high. Stack tortillas and wrap in heavy-duty foil.
Combine oil, 1 teaspoon powdered chipotle and 1/2 teaspoon salt in a small dish. Rub into both sides of steak. Place the tortilla stack on the coolest part of the grill or upper warming rack, if possible, and heat, flipping once, until warmed through and very pliable. Meanwhile, grill the steak for 4 to 6 minutes per side for medium, or until desired doneness. Grill pineapple rings until moderately charred, 1 to 2 minutes per side. Remove the tortillas, steak and pineapple from the grill. Let the steak rest for at least 5 minutes before very thinly slicing crosswise into strips.
Meanwhile, dice the pineapple and transfer to a medium bowl. Add bell pepper, onion, cilantro, vinegar, the remaining pinch of chipotle and the remaining 1/2 teaspoon salt; toss to combine. Serve the sliced steak in the warm tortillas with the pineapple salsa.