In a small bowl whisk together vinegar, oil, mustard, salt, and pepper. Pour half the vinegar mixture into a large bowl for the salad. Pour remaining vinegar mixture into a medium bowl for the pork.
Add rosemary and fennel seeds to the vinegar mixture in the medium bowl for the pork. Using a thin, sharp knife, remove the thin silver skin membrane from the pork tenderloin. If the tenderloin is very thin on one end, fold the end over onto itself and use a short length of kitchen string to tie around the end to keep it folded over.
Add pork to the marinade that has the rosemary added. Turn pork to fully coat with the marinade. Cover; marinate pork in the refrigerator for 1 to 2 hours.
Meanwhile, cut tops off the fennel bulb. Cut a thin slice off the base of the bulb. Cut bulb in half; cut out the core and discard. Cut remaining bulb into very thin slices. Add to the large bowl with other half of the vinegar mixture. Add cucumber and onion. Toss vegetables until well coated with the vinegar mixture. Cover; chill up to 3 hours, stirring once or twice.
If using bamboo skewers, soak skewers in enough water to cover for 30 minutes. When ready to grill, thread tomatoes and olives evenly onto skewers.
Remove pork from the marinade; discard remaining marinade. For a charcoal or gas grill, grill pork over medium coals or medium heat for 18 to 22 minutes or until an instant-read thermometer inserted in thickest part of the pork registers 145°Transfer pork to a serving platter; cover with foil. Let rest for 3 to 5 minutes before serving.
While pork is resting, add tomato kabobs to the grill over medium coals or heat. Grill for 3 to 4 minutes or until tomatoes are just softened and olives and tomatoes are starting to brown, turning kabobs once halfway through grilling.
Just before serving, add parsley to the chilled cucumber salad; toss to combine. Slice pork and serve with salad and tomato kabobs.