Backlash would've had a lot more dating experience than Tesla did when they got together, but let's be honest all that did was stroke his ego. They could have had a puppy love dating period that turned into friendship after they realized they were better as friends than lovers? Backlash tends to get antsy in relationships, so he could have been the reason things ended romantically between them and if it fits that could have soured their dynamic for a bit until they worked it out in the Inferno? If they've stayed close, Tesla could be one of the few people Backlash has told about the lust/hate thing he has for his handler, Leah Steele.