Different behaviour in hosted demo than local

I'm working on a similar application like your hosted demo. When I use the same objectId for two different objects it still works great in the demo, but not at all when running it myself.

It looks good for a single point:

But for one point on the human and one point on the car it looks like this:

Meanwhile in your demo:

What is the reason for that behaviour? I understand that we should just use separate objectId's but I'm nevertheless interested why it looks so much better in your demo.

EDIT: Actually there is a very valid use case for merging the objects. If you want to classify something as foreground and background then using two objects will have gaps between the objects. This way they are automatically closed.

Any insight is greatly appreciated!