Unless you have discovered a perpetual motion machine, there is no way your DN70 can run at 2500 lumen for 90 minutes on a 4500mAh battery. Do the math. 4500 x 3.7=16650. The capacity of the battery is 16650 mwh, or 16.65 watt hours. 2500 lumens is going to require the battery supply at least 20 watts, and probably closer to 25 watts, so 90 minutes at 2500 lumens will require 30 to 37.5 watt hours. Obviously you are NOT going to get that out of a battery with 16.65 watt hour capacity. There are two things that come into play in how long this thing will run. First the 3000mAh battery probably has more ‘voltage sag’ at 7 amps draw (roughly what is required for the full 2500 lumen output) than a 4500mAh cell, so the losses in the battery and in the driver are likely to be considerably higher in the TM03 than they are in the DN70. The second thing that happens is how long does it take before the thermal management steps down the output to the LED. The only way your TM70 can run for 90 minutes is if the LED steps down substantially. As the math clearly shows, full power output for 90 minutes requires roughly twice the actual energy capacity of the battery. So obviously the DN70 reduces the output substantially at some point, almost certainly due to thermal management, and that lower output substantially extends the run time.
As for the 20amps, I have no idea where you got that number from. 20 amps at 3.7 volts is 74 watts (which is roughly 3 times what is actually needed), it doubtful even your 4500mAh cell can do that without substantial voltage sag, and overheating, a 3000mAh battery will run for even less time. Less capacity, more sag, and less thermal mass. Id be willing to bet that the 15 minute time on the TM03 is from Thermal management not battery capacity.