To be fair, the rule applies whether you have Ambidexterity or not. That's completely separate ruleset from using two weapons at once.
I know. What I meant when talking about ambidexterity before was that it would make alot of sense that you were aiming slower because not only are you 'splitting your die pool' so to speak, you also would have had an extra -2 on your off hand.
Since what you said was basically "I aimed a single laser in 1 second, but two lasers took me 4-5 seconds" I was trying to say "Well yes, it took you longer because not only are you at half your skill, you have an added penalty for using your off hand." Which is why I keep reitterating that your experiment shows that it takes you longer to aim two 'guns' than one, but it doesn't show if aiming two 'guns' with lasers is the same speed or not as aiming two 'guns' without lasers.
Maybe do this: Give yourself about 5 seconds to aim with both laser pointers off, then hit the button and see how accurate you are. Then try to aim for your target with both pointers on, and see if you are any more accurate with the pointers on after five seconds than with them off. If so then obviously the 'laser sights' helped you aim. Now granted 5 seconds is a long time in the SR universe, but you aren't a superhuman cyborg or adept (I'm reasonably sure). I suppose you could try lowering it down to 3 seconds to simulate a combat turn with, quite obviously, no additional IPs on your part.