I dont really understand how you can not grasp this concepts

Do you realize what a simulation is ?

You use a simulation just in case some " inputs " are not perfectly known otherwise you would simply put them in some equations

It is not definitly true that they are completely arbritraty

You dont know the exact value of these inputs but you know for example their upper limits

You assign different values to these uncertain inputs provided they are within the bounds of the above mentioned limiits

Then you run your simulation and you can get different scenarios corresponding to different values of these inputs

If none of these scenarios is realistic than the original claim is false

A simulation is a widly used scientific method to tackle those kind of complex problems containing many parameters with an high degree of uncertainity

Mr Bjork did not use arbitrary inputs he explains his choice

Moreover you continue missing one point

The result of the simulation is so absurd that even using more favourable inputs, within the bound of the physical laws, it would lead in any case to an absurd scenario

This is the reason why he did not repeat the simulation using more probes

Read the article , please read it