Well like the Tutorial states, it wipes installed titles and most of the saves but still not everything. After a NAND backup made before hacking, this would take the #2 spot in terms of being safe. Plus unlike a NAND backup, it involves a lot more steps that makes me question how far people would go to avoid getting banned considering that online is paid for.
Since I already have a dirty NAND and there is no other way to undo because my 1st clean NAND backup gave me a softbrick switch, I gave this guide a try. After a 10mins operation, I reinitialized, tested eshop and still working (not banned yet), created a fresh semi clean NAND, then CFW.. But yea, online services will no longer be free so I really don't care now if I get a ban..
After 1 month, I will try to restore my semi clean NAND and test eshop to see if I am banned. Whether I am or not, I'll fill up your form and share it here.
Thanks for your kind answers.