Where did you read what I wrote about hacking SLIP39?
I just wrote that having access to one of the parts of the backup you can get information about share groups and the group threshold. If you do not understand this point, then create a multi-share backup using the converter, publish one part of it here, and I will provide you with information about share groups and the group threshold.

I'm not criticizing the SLIP39 standard, I created a post for people who buy a Trezor wallet and will be faced with choosing a backup type when setting it up.