@B-HKD
Your statement
"EK is to date the only operator that purchased the the AUX tank option on the -200LR"
is not true.
Air India also purchased 4 x 200LRs with AUX tanks. VT-ALF/G/H and VT-ALE(current EY A6-LRE).
Don't know if EY kept the aux tank or not, but at least 3x200LRs STILL have aux tanks.
Originally VT-ALD intended to be the worlds first longest range aircraft, but certification delays changed plans and VT-ALD was delivered without aux tank.