They do that in real life when its immediately clear for the barriers to go down. If there’s an obstruction the alarm will still sound but the barriers will stay up until its clear and the train will be signalled to stop
The level crossings are way too quick, they lower the barriers as soon as the red lights go on and their lowering speed is too high, normally on UK level crossings, once the amber light has switched for the red lights there are a few seconds before the barriers start to go down, and their lowering speed is lower, the full sequence between the moment the crossing triggers and the gates are fully down should be around 30 seconds, in TSW2 it's more like 5 seconds