Where in that question is the 2nd laptop? Answer: Not mentioned.
But regardless1 computer USB out to 2 USB inputs. That completely depends on the drive capability
of the USB out computer. All you can do is try it. Report back your results as required by FCC law.
Kidding, but I would like to know if it does work, I have seen this Q before.
You are talking about using some sort of a USB splitter? Most USB devices are used to add more ports or to extend the ports, not to share a single peripheral among multiple systems. I think all the USB sharing devices I have seen have a selector for each system, not simultaneous use.
If you want to test something that needs the same input at the same time to both systems, you may be able to use an analog 3.5mm headset with an audio splitter running to both systems. Or just setup a mic on each system, mute the speakers to prevent feedback and talk into the two mics side by side.