You would be correct if the code worked differently. I'll use an example by your demonstration.
.......|..|....... Would NOT work
.......|.|........ Would work
.......|.|.|.|.... Would also work
.......|........... Self Explanatory (Harvest + variants <3)
The second last one however is subjectable. Since mines curve with 'gravity', how far they move XY coords is different. When moving straight in one direction, they'll skip EXACTLY ONE gg2 pixel every frame. Up/Down is harder but still possible, while Left/Right is pretty easy. It depends on BOTH distance and angle since full 360 aim, however it have to be exact distance if just 90° aiming. Yet with the curve, they'll eventually not skip an entire gg2 pixel.
This is Entities though, I haven't seem to be able to get them through 1px diagonal collision like rockets and rifle's laser
Also,
with(RedTeamGate){visible=1}
with(RedTeamGate2){visible=1}
Sorry 3px not 4px, still literally impossible.
Edit: Since explaining this now. It's going to be abused like the old Granary exploit.