Being able to observe all inputs sources at the same time requires extra hardware(more utilisation of the FPGA resources), considering only one input is connected to the display at a time. So it's probable that the check is sequential.
Maybe the downside is that Bob will observe that others express displeasure at his behavior, having let down their expectations(maybe unreasonable) of him. Now Bob isn't callous by nature so this will weigh upon his conscience.