He's talking about the fact that you can slow the t1 bomber down, fire, and slow it down again before it moves. If you're good with micro, the bomber can barely move (it takes much practice). Rinse and repeat, in this case Solace used it for an early engy/pgen snipe.
Slowing down the bomber to get radar and select the target is a key part of the early micro. A speed limit will hurt the bomber's responsiveness in those situations. If you want to address the behavior in that replay, put a reload timer on the bomber. That caps the DPS without making the unit not fire at all in some situations
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That said, I don't think this should be changed at all - it's not broken. This action adds depth to the micro that is not easy to do, costly in terms of attention needed with a fast loss of the bomber if mobile AA is on the ground. The reason TA4life hurt so much was because he had no AA at all.
Here's the replay.