Well, I did not read the law in detail, but I am pretty sure, that tampering with evidence is not included and still forbidden with the threat of criminal investigation for the officers doing it.

What is allowed here, is hacking for the police. That necessarily can include changing files on the target computers (e.g. deleting logs) - this is the way I read this. And I would see the point in it - if it really only get applied in serious crimes like terrorism to catch the whole network for example. (back to trust)

But yes, it maybe makes it more easy to tamper undetected with evidence in sneaky ways, but not if for example you would log the hacking activities by default of the police. In fact, I strongly believe that this should be done, but doubt, it will be.