As explained so many times on the forum, GSX vehicles are not really aware of each other because, if they did as you are suggesting, a whole new class of problems might appear, like deadlocks on the limited space in a parking.
In addition to that, being aware of each other would mean that each vehicle would have to constantly spam the sim with Simconnect commands, causing stuttering, loss of fps and possibly disruption to other add-ons that also communicates with the sim in real time ( weather engines, fsuipc, etc. )
So, we try to prevent their conflict by acting in the startup times and their position. But it cannot work everywhere, because it depends by the scenery too. Which is why, you are being given the ability to customize their starting positions precisely, which usually can fix the few remaining cases of vehicles clashing into each other.
