deviating slightly from pure open source principles

saying that prohibiting redistribution is just "deviating slightly from pure open source principles" is like saying that a dish with a bit of meat in it is just "deviating slightly" from a vegetarian recipe.

if you saw a restaurant labeling their food as vegetarian because their dishes were based on vegetarian recipes, but had some meat added, would you say that it seems like their intentions are good?

to protect their users from scammy clones

As I said in another comment, the way free open source software projects should (and can, and do) generally do this is using trademark law. He could license it under any free software license but require derivatives to change the name to avoid misleading or confusing users. This is what Firefox and many other projects do.

TBH we’re not really into strictly following the letter of the law in the pirate community

In the video announcing the project Louis Rossmann explicitly says he intends to vigorously enforce this license. Since it is a copyright license, the only ways of actually enforcing it are to send DMCA takedowns and/or sue people for copyright infringement.